Name: Prior Analytics, Book II
Author: Aristotle

Ross (OCT, 1964) · Jenkinson (1928)

Greek line numbers are exact. The translations carry no Bekker numbers of their own, so those beside the English are aligned to the Greek: upright = fixed (anchored to this point in the text), italic grey = approximate (interpolated estimate).

Book 2,Chapter 1 (52b38–53b3)

52b

Ἐν πόσοις μὲν οὖν σχήμασι καὶ διὰ ποίων καὶ πόσων

προτάσεων καὶ πότε καὶ πῶς γίνεται συλλογισμός,

40 ἔτι δ' εἰς ποῖα βλεπτέον ἀνασκευάζοντι καὶ κατασκευάζοντι,

38We have already explained the number of the figures, the character and number of the premisses, when and how a syllogism is formed; 40further what we must look for when a refuting and establishing propositions, and how we should investigate a given problem in any branch of inquiry, also by what means we shall obtain principles appropriate to each subject.

53a

1 καὶ πῶς δεῖ ζητεῖν περὶ τοῦ προκειμένου καθ' ὁποιανοῦν

μέθοδον, ἔτι δὲ διὰ ποίας ὁδοῦ ληψόμεθα τὰς περὶ

ἕκαστον ἀρχάς, ἤδη διεληλύθαμεν. ἐπεὶ δ' οἱ μὲν καθόλου

τῶν συλλογισμῶν εἰσὶν οἱ δὲ κατὰ μέρος, οἱ μὲν καθόλου

5 πάντες αἰεὶ πλείω συλλογίζονται, τῶν δ' ἐν μέρει οἱ μὲν

κατηγορικοὶ πλείω, οἱ δ' ἀποφατικοὶ τὸ συμπέρασμα μόνον.

αἱ μὲν γὰρ ἄλλαι προτάσεις ἀντιστρέφουσιν, ἡ δὲ στερητικὴ

οὐκ ἀντιστρέφει. τὸ δὲ συμπέρασμα τὶ κατά τινός

ἐστιν, ὥσθ' οἱ μὲν ἄλλοι συλλογισμοὶ πλείω συλλογίζονται,

10 οἷον εἰ τὸ Α δέδεικται παντὶ τῷ Β ἢ τινί, καὶ τὸ Β

τινὶ τῷ Α ἀναγκαῖον ὑπάρχειν, καὶ εἰ μηδενὶ τῷ Β τὸ Α,

οὐδὲ τὸ Β οὐδενὶ τῷ Α, τοῦτο δ' ἕτερον τοῦ ἔμπροσθεν· εἰ δὲ

τινὶ μὴ ὑπάρχει, οὐκ ἀνάγκη καὶ τὸ Β τινὶ τῷ Α μὴ

ὑπάρχειν· ἐνδέχεται γὰρ παντὶ ὑπάρχειν.

15 Αὕτη μὲν οὖν κοινὴ πάντων αἰτία, τῶν τε καθόλου

καὶ τῶν κατὰ μέρος· ἔστι δὲ περὶ τῶν καθόλου καὶ ἄλλως

εἰπεῖν. ὅσα γὰρ ἢ ὑπὸ τὸ μέσον ἢ ὑπὸ τὸ συμπέρασμά

ἐστιν, ἁπάντων ἔσται ὁ αὐτὸς συλλογισμός, ἐὰν τὰ μὲν ἐν

τῷ μέσῳ τὰ δ' ἐν τῷ συμπεράσματι τεθῇ, οἷον εἰ τὸ Α Β

20 συμπέρασμα διὰ τοῦ Γ, ὅσα ὑπὸ τὸ Β ἢ τὸ Γ ἐστίν,

ἀνάγκη κατὰ πάντων λέγεσθαι τὸ Α· εἰ γὰρ τὸ Δ ἐν ὅλῳ

τῷ Β, τὸ δὲ Β ἐν τῷ Α, καὶ τὸ Δ ἔσται ἐν τῷ Α· πάλιν

εἰ τὸ Ε ἐν ὅλῳ τῷ Γ, τὸ δὲ Γ ἐν τῷ Α, καὶ τὸ Ε

ἐν τῷ Α ἔσται. ὁμοίως δὲ καὶ εἰ στερητικὸς ὁ συλλογισμός.

25 ἐπὶ δὲ τοῦ δευτέρου σχήματος τὸ ὑπὸ τὸ συμπέρασμα μόνον

ἔσται συλλογίσασθαι, οἷον εἰ τὸ Α τῷ Β μηδενί, τῷ

δὲ Γ παντί· συμπέρασμα ὅτι οὐδενὶ τῷ Γ τὸ Β. εἰ δὴ τὸ

Δ ὑπὸ τὸ Γ ἐστί, φανερὸν ὅτι οὐχ ὑπάρχει αὐτῷ τὸ Β·

τοῖς δ' ὑπὸ τὸ Α ὅτι οὐχ ὑπάρχει, οὐ δῆλον διὰ τοῦ συλλογισμοῦ.

30 καίτοι οὐχ ὑπάρχει τῷ Ε, εἰ ἔστιν ὑπὸ τὸ Α·

ἀλλὰ τὸ μὲν τῷ Γ μηδενὶ ὑπάρχειν τὸ Β διὰ τοῦ συλλογισμοῦ

δέδεικται, τὸ δὲ τῷ Α μὴ ὑπάρχειν ἀναπόδεικτον

εἴληπται, ὥστ' οὐ διὰ τὸν συλλογισμὸν συμβαίνει τὸ

Β τῷ Ε μὴ ὑπάρχειν. ἐπὶ δὲ τῶν ἐν μέρει τῶν μὲν ὑπὸ

35 τὸ συμπέρασμα οὐκ ἔσται τὸ ἀναγκαῖον (οὐ γὰρ γίνεται

συλλογισμός, ὅταν αὕτη ληφθῇ ἐν μέρει), τῶν δ' ὑπὸ τὸ

μέσον ἔσται πάντων, πλὴν οὐ διὰ τὸν συλλογισμόν· οἷον εἰ

τὸ Α παντὶ τῷ Β, τὸ δὲ Β τινὶ τῷ Γ· τοῦ μὲν γὰρ ὑπὸ

τὸ Γ τεθέντος οὐκ ἔσται συλλογισμός, τοῦ δ' ὑπὸ τὸ Β ἔσται,

40 ἀλλ' οὐ διὰ τὸν προγεγενημένον. ὁμοίως δὲ κἀπὶ τῶν ἄλλων

σχημάτων· τοῦ μὲν γὰρ ὑπὸ τὸ συμπέρασμα οὐκ ἔσται,

1Since some syllogisms are universal, others particular, 5all the universal syllogisms give more than one result, and of particular syllogisms the affirmative yield more than one, the negative yield only the stated conclusion. For all propositions are convertible save only the particular negative: and the conclusion states one definite thing about another definite thing. Consequently all syllogisms save the particular negative yield more than one conclusion, 10e.g. if A has been proved to to all or to some B, then B must belong to some A: and if A has been proved to belong to no B, then B belongs to no A. This is a different conclusion from the former. But if A does not belong to some B, it is not necessary that B should not belong to some A: for it may possibly belong to all A.
15This then is the reason common to all syllogisms whether universal or particular. But it is possible to give another reason concerning those which are universal. For all the things that are subordinate to the middle term or to the conclusion may be proved by the same syllogism, if the former are placed in the middle, the latter in the conclusion; e.g. if the conclusion AB 20is proved through C, whatever is subordinate to B or C must accept the predicate A: for if D is included in B as in a whole, and B is included in A, then D will be included in A. Again if E is included in C as in a whole, and C is included in A, then E will be included in A. Similarly if the syllogism is negative. 25In the second figure it will be possible to infer only that which is subordinate to the conclusion, e.g. if A belongs to no B and to all C; we conclude that B belongs to no C. If then D is subordinate to C, clearly B does not belong to it. But that B does not belong to what is subordinate to A is not clear by means of the syllogism. 30And yet B does not belong to E, if E is subordinate to A. But while it has been proved through the syllogism that B belongs to no C, it has been assumed without proof that B does not belong to A, consequently it does not result through the syllogism that B does not belong to E.
But in particular syllogisms 35there will be no necessity of inferring what is subordinate to the conclusion (for a syllogism does not result when this premiss is particular), but whatever is subordinate to the middle term may be inferred, not however through the syllogism, e.g. if A belongs to all B and B to some C. Nothing can be inferred about that which is subordinate to C; something can be inferred about that which is subordinate to B, 40but not through the preceding syllogism. Similarly in the other figures.

53b

1 θατέρου δ' ἔσται, πλὴν οὐ διὰ τὸν συλλογισμόν, ᾗ καὶ ἐν

τοῖς καθόλου ἐξ ἀναποδείκτου τῆς προτάσεως τὰ ὑπὸ τὸ

μέσον ἐδείκνυτο· ὥστ' ἢ οὐδ' ἐκεῖ ἔσται ἢ καὶ ἐπὶ τούτων.

1That which is subordinate to the conclusion cannot be proved; the other subordinate can be proved, only not through the syllogism, just as in the universal syllogisms what is subordinate to the middle term is proved (as we saw) from a premiss which is not demonstrated: consequently either a conclusion is not possible in the case of universal syllogisms or else it is possible also in the case of particular syllogisms.

Book 2,Chapter 2 (53b4–55b2)

Ἔστι μὲν οὖν οὕτως ἔχειν ὥστ' ἀληθεῖς εἶναι τὰς προτάσεις

5 δι' ὧν ὁ συλλογισμός, ἔστι δ' ὥστε ψευδεῖς, ἔστι δ'

ὥστε τὴν μὲν ἀληθῆ τὴν δὲ ψευδῆ. τὸ δὲ συμπέρασμα ἢ

ἀληθὲς ἢ ψεῦδος ἐξ ἀνάγκης. ἐξ ἀληθῶν μὲν οὖν οὐκ ἔστι

ψεῦδος συλλογίσασθαι, ἐκ ψευδῶν δ' ἔστιν ἀληθές, πλὴν

οὐ διότι ἀλλ' ὅτι· τοῦ γὰρ διότι οὐκ ἔστιν ἐκ ψευδῶν συλλογισμός·

10 δι' ἣν δ' αἰτίαν, ἐν τοῖς ἑπομένοις λεχθήσεται.

Πρῶτον μὲν οὖν ὅτι ἐξ ἀληθῶν οὐχ οἷόν τε ψεῦδος

συλλογίσασθαι, ἐντεῦθεν δῆλον. εἰ γὰρ τοῦ Α ὄντος ἀνάγκη

τὸ Β εἶναι, τοῦ Β μὴ ὄντος ἀνάγκη τὸ Α μὴ εἶναι. εἰ οὖν

ἀληθές ἐστι τὸ Α, ἀνάγκη τὸ Β ἀληθὲς εἶναι, ἢ συμβήσεται

15 τὸ αὐτὸ ἅμα εἶναί τε καὶ οὐκ εἶναι· τοῦτο δ' ἀδύνατον.

μὴ ὅτι δὲ κεῖται τὸ Α εἷς ὅρος, ὑποληφθήτω ἐνδέχεσθαι

ἑνός τινος ὄντος ἐξ ἀνάγκης τι συμβαίνειν· οὐ γὰρ

οἷόν τε· τὸ μὲν γὰρ συμβαῖνον ἐξ ἀνάγκης τὸ συμπέρασμά

ἐστι, δι' ὧν δὲ τοῦτο γίνεται ἐλαχίστων, τρεῖς ὅροι,

20 δύο δὲ διαστήματα καὶ προτάσεις. εἰ οὖν ἀληθές, ᾧ τὸ Β

ὑπάρχει, τὸ Α παντί, ᾧ δὲ τὸ Γ, τὸ Β, ᾧ τὸ Γ, ἀνάγκη

τὸ Α ὑπάρχειν καὶ οὐχ οἷόν τε τοῦτο ψεῦδος εἶναι· ἅμα

γὰρ ὑπάρξει ταὐτὸ καὶ οὐχ ὑπάρξει. τὸ οὖν Α ὥσπερ ἓν κεῖται,

δύο προτάσεις συλληφθεῖσαι. ὁμοίως δὲ καὶ ἐπὶ τῶν

25 στερητικῶν ἔχει· οὐ γὰρ ἔστιν ἐξ ἀληθῶν δεῖξαι ψεῦδος.

Ἐκ ψευδῶν δ' ἀληθὲς ἔστι συλλογίσασθαι καὶ ἀμφοτέρων

τῶν προτάσεων ψευδῶν οὐσῶν καὶ τῆς μιᾶς, ταύτης

δ' οὐχ ὁποτέρας ἔτυχεν ἀλλὰ τῆς δευτέρας, ἐάνπερ

ὅλην λαμβάνῃ ψευδῆ· μὴ ὅλης δὲ λαμβανομένης ἔστιν

30 ὁποτερασοῦν. ἔστω γὰρ τὸ Α ὅλῳ τῷ Γ ὑπάρχον, τῷ δὲ

Β μηδενί, μηδὲ τὸ Β τῷ Γ. ἐνδέχεται δὲ τοῦτο, οἷον λίθῳ

οὐδενὶ ζῷον, οὐδὲ λίθος οὐδενὶ ἀνθρώπῳ. ἐὰν οὖν ληφθῇ τὸ Α

παντὶ τῷ Β καὶ τὸ Β παντὶ τῷ Γ, τὸ Α παντὶ τῷ Γ

ὑπάρξει, ὥστ' ἐξ ἀμφοῖν ψευδῶν ἀληθὲς τὸ συμπέρασμα·

35 πᾶς γὰρ ἄνθρωπος ζῷον. ὡσαύτως δὲ καὶ τὸ στερητικόν.

ἔστι γὰρ τῷ Γ μήτε τὸ Α ὑπάρχειν μηδενὶ μήτε τὸ

Β, τὸ μέντοι Α τῷ Β παντί, οἷον ἐὰν τῶν αὐτῶν ὅρων ληφθέντων

μέσον τεθῇ ὁ ἄνθρωπος· λίθῳ γὰρ οὔτε ζῷον οὔτε

ἄνθρωπος οὐδενὶ ὑπάρχει, ἀνθρώπῳ δὲ παντὶ ζῷον. ὥστ' ἐὰν

40 ᾧ μὲν ὑπάρχει, λάβῃ μηδενὶ ὑπάρχειν, ᾧ δὲ μὴ ὑπάρχει,

παντὶ ὑπάρχειν, ἐκ ψευδῶν ἀμφοῖν ἀληθὲς ἔσται τὸ συμπέρασμα.

4It is possible for the premisses of the syllogism to be true, 5or to be false, or to be the one true, the other false. The conclusion is either true or false necessarily. From true premisses it is not possible to draw a false conclusion, but a true conclusion may be drawn from false premisses, true however only in respect to the fact, not to the reason. The reason cannot be established from false premisses: 10why this is so will be explained in the sequel.
First then that it is not possible to draw a false conclusion from true premisses, is made clear by this consideration. If it is necessary that B should be when A is, it is necessary that A should not be when B is not. If then A is true, B must be true: otherwise it will turn out that 15the same thing both is and is not at the same time. But this is impossible. Let it not, because A is laid down as a single term, be supposed that it is possible, when a single fact is given, that something should necessarily result. For that is not possible. For what results necessarily is the conclusion, and the means by which this comes about are at the least three terms, 20and two relations of subject and predicate or premisses. If then it is true that A belongs to all that to which B belongs, and that B belongs to all that to which C belongs, it is necessary that A should belong to all that to which C belongs, and this cannot be false: for then the same thing will belong and not belong at the same time. So A is posited as one thing, being two premisses taken together. The same holds good of 25negative syllogisms: it is not possible to prove a false conclusion from true premisses.
But from what is false a true conclusion may be drawn, whether both the premisses are false or only one, provided that this is not either of the premisses indifferently, if it is taken as wholly false: but if the premiss is not taken as wholly false, it does not matter which of the two is false. 30(1) Let A belong to the whole of C, but to none of the Bs, neither let B belong to C. This is possible, e.g. animal belongs to no stone, nor stone to any man. If then A is taken to belong to all B and B to all C, A will belong to all C; consequently though both the premisses are false the conclusion is true: 35for every man is an animal. Similarly with the negative. For it is possible that neither A nor B should belong to any C, although A belongs to all B, e.g. 40if the same terms are taken and man is put as middle: for neither animal nor man belongs to any stone, but animal belongs to every man.

54a

1 ὁμοίως δὲ δειχθήσεται καὶ ἐὰν ἐπί τι ψευδὴς

ἑκατέρα ληφθῇ. Ἐὰν δ' ἡ ἑτέρα τεθῇ ψευδής, τῆς μὲν πρώτης

ὅλης ψευδοῦς οὔσης, οἷον τῆς Α Β, οὐκ ἔσται τὸ συμπέρασμα

ἀληθές, τῆς δὲ Β Γ ἔσται. λέγω δ' ὅλην ψευδῆ τὴν

5 ἐναντίαν, οἷον εἰ μηδενὶ ὑπάρχον παντὶ εἴληπται ἢ εἰ παντὶ

μηδενὶ ὑπάρχειν. ἔστω γὰρ τὸ Α τῷ Β μηδενὶ ὑπάρχον, τὸ

δὲ Β τῷ Γ παντί. ἂν δὴ τὴν μὲν Β Γ πρότασιν λάβω

ἀληθῆ, τὴν δὲ τὸ Α Β ψευδῆ ὅλην, καὶ παντὶ ὑπάρχειν τῷ

Β τὸ Α, ἀδύνατον τὸ συμπέρασμα ἀληθὲς εἶναι· οὐδενὶ γὰρ

10 ὑπῆρχε τῶν Γ, εἴπερ ᾧ τὸ Β, μηδενὶ τὸ Α, τὸ δὲ Β παντὶ

τῷ Γ. ὁμοίως δ' οὐδ' εἰ τὸ Α τῷ Β παντὶ ὑπάρχει καὶ τὸ

Β τῷ Γ, ἐλήφθη δ' ἡ μὲν τὸ Β Γ ἀληθὴς πρότασις, ἡ

δὲ τὸ Α Β ψευδὴς ὅλη, καὶ μηδενὶ ᾧ τὸ Β, τὸ Α—τὸ συμπέρασμα

ψεῦδος ἔσται· παντὶ γὰρ ὑπάρξει τῷ Γ τὸ Α,

15 εἴπερ ᾧ τὸ Β, παντὶ τὸ Α, τὸ δὲ Β παντὶ τῷ Γ. φανερὸν

οὖν ὅτι τῆς πρώτης ὅλης λαμβανομένης ψευδοῦς, ἐάν τε καταφατικῆς

ἐάν τε στερητικῆς, τῆς δ' ἑτέρας ἀληθοῦς, οὐ γίνεται

ἀληθὲς τὸ συμπέρασμα. Μὴ ὅλης δὲ λαμβανομένης

ψευδοῦς ἔσται. εἰ γὰρ τὸ Α τῷ μὲν Γ παντὶ ὑπάρχει τῷ

20 δὲ Β τινί, τὸ δὲ Β παντὶ τῷ Γ, οἷον ζῷον κύκνῳ μὲν παντὶ

λευκῷ δὲ τινί, τὸ δὲ λευκὸν παντὶ κύκνῳ, ἐὰν ληφθῇ τὸ Α

παντὶ τῷ Β καὶ τὸ Β παντὶ τῷ Γ, τὸ Α παντὶ τῷ Γ ὑπάρξει

ἀληθῶς· πᾶς γὰρ κύκνος ζῷον. ὁμοίως δὲ καὶ εἰ στερητικὸν

εἴη τὸ Α Β· ἐγχωρεῖ γὰρ τὸ Α τῷ μὲν Β τινὶ ὑπάρχειν

25 τῷ δὲ Γ μηδενί, τὸ δὲ Β παντὶ τῷ Γ, οἷον ζῷον τινὶ λευκῷ

χίονι δ' οὐδεμιᾷ, λευκὸν δὲ πάσῃ χιόνι. εἰ οὖν ληφθείη

τὸ μὲν Α μηδενὶ τῷ Β, τὸ δὲ Β παντὶ τῷ Γ, τὸ Α οὐδενὶ

τῷ Γ ὑπάρξει. Ἐὰν δ' ἡ μὲν Α Β πρότασις ὅλη ληφθῇ

ἀληθής, ἡ δὲ Β Γ ὅλη ψευδής, ἔσται συλλογισμὸς ἀληθής·

30 οὐδὲν γὰρ κωλύει τὸ Α τῷ Β καὶ τῷ Γ παντὶ ὑπάρχειν,

τὸ μέντοι Β μηδενὶ τῷ Γ, οἷον ὅσα τοῦ αὐτοῦ γένους

εἴδη μὴ ὑπ' ἄλληλα· τὸ γὰρ ζῷον καὶ ἵππῳ καὶ ἀνθρώπῳ

ὑπάρχει, ἵππος δ' οὐδενὶ ἀνθρώπῳ. ἐὰν οὖν ληφθῇ τὸ Α

παντὶ τῷ Β καὶ τὸ Β παντὶ τῷ Γ, ἀληθὲς ἔσται τὸ συμπέρασμα,

35 ψευδοῦς ὅλης οὔσης τῆς Β Γ προτάσεως. ὁμοίως

δὲ καὶ στερητικῆς οὔσης τῆς Α Β προτάσεως. ἐνδέχεται γὰρ

τὸ Α μήτε τῷ Β μήτε τῷ Γ μηδενὶ ὑπάρχειν, μηδὲ τὸ Β

μηδενὶ τῷ Γ, οἷον τοῖς ἐξ ἄλλου γένους εἴδεσι τὸ γένος·

τὸ γὰρ ζῷον οὔτε μουσικῇ οὔτ' ἰατρικῇ ὑπάρχει, οὐδ'

1Consequently if one term is taken to belong to none of that to which it does belong, and the other term is taken to belong to all of that to which it does not belong, though both the premisses are false the conclusion will be true. (2) A similar proof may be given if each premiss is partially false.
(3) But if one only of the premisses is false, when the first premiss is wholly false, e.g. AB, the conclusion will not be true, but if the premiss BC is wholly false, a true conclusion will be possible. I mean by 'wholly false' 5the contrary of the truth, e.g. if what belongs to none is assumed to belong to all, or if what belongs to all is assumed to belong to none. Let A belong to no B, and B to all C. If then the premiss BC which I take is true, and the premiss AB is wholly false, viz. that A belongs to all B, it is impossible that the conclusion should be true: 10for A belonged to none of the Cs, since A belonged to nothing to which B belonged, and B belonged to all C. Similarly there cannot be a true conclusion if A belongs to all B, and B to all C, but while the true premiss BC is assumed, the wholly false premiss AB is also assumed, viz. that A belongs to nothing to which B belongs: here the conclusion must be false. For A will belong to all C, 15since A belongs to everything to which B belongs, and B to all C. It is clear then that when the first premiss is wholly false, whether affirmative or negative, and the other premiss is true, the conclusion cannot be true.
(4) But if the premiss is not wholly false, a true conclusion is possible. For if A belongs to all C 20and to some B, and if B belongs to all C, e.g. animal to every swan and to some white thing, and white to every swan, then if we take as premisses that A belongs to all B, and B to all C, A will belong to all C truly: for every swan is an animal. Similarly if the statement AB is negative. For it is possible that A should belong to some B 25and to no C, and that B should belong to all C, e.g. animal to some white thing, but to no snow, and white to all snow. If then one should assume that A belongs to no B, and B to all C, then will belong to no C.
(5) But if the premiss AB, which is assumed, is wholly true, and the premiss BC is wholly false, a true syllogism will be possible: 30for nothing prevents A belonging to all B and to all C, though B belongs to no C, e.g. 35these being species of the same genus which are not subordinate one to the other: for animal belongs both to horse and to man, but horse to no man.

54b

1 ἡ μουσικὴ ἰατρικῇ. ληφθέντος οὖν τοῦ μὲν Α μηδενὶ τῷ Β,

τοῦ δὲ Β παντὶ τῷ Γ, ἀληθὲς ἔσται τὸ συμπέρασμα. καὶ εἰ

μὴ ὅλη ψευδὴς ἡ Β Γ ἀλλ' ἐπί τι, καὶ οὕτως ἔσται τὸ συμπέρασμα

ἀληθές. οὐδὲν γὰρ κωλύει τὸ Α καὶ τῷ Β καὶ τῷ

5 Γ ὅλῳ ὑπάρχειν, τὸ μέντοι Β τινὶ τῷ Γ, οἷον τὸ γένος τῷ

εἴδει καὶ τῇ διαφορᾷ· τὸ γὰρ ζῷον παντὶ ἀνθρώπῳ καὶ

παντὶ πεζῷ, ὁ δ' ἄνθρωπος τινὶ πεζῷ καὶ οὐ παντί. εἰ οὖν τὸ

Α παντὶ τῷ Β καὶ τὸ Β παντὶ τῷ Γ ληφθείη, τὸ Α παντὶ

τῷ Γ ὑπάρξει· ὅπερ ἦν ἀληθές. ὁμοίως δὲ καὶ στερητικῆς

10 οὔσης τῆς Α Β προτάσεως. ἐνδέχεται γὰρ τὸ Α μήτε τῷ Β

μήτε τῷ Γ μηδενὶ ὑπάρχειν, τὸ μέντοι Β τινὶ τῷ Γ, οἷον

τὸ γένος τῷ ἐξ ἄλλου γένους εἴδει καὶ διαφορᾷ· τὸ γὰρ

ζῷον οὔτε φρονήσει οὐδεμιᾷ ὑπάρχει οὔτε θεωρητικῇ, ἡ δὲ

φρόνησις τινὶ θεωρητικῇ. εἰ οὖν ληφθείη τὸ μὲν Α μηδενὶ τῷ

15 Β, τὸ δὲ Β παντὶ τῷ Γ, οὐδενὶ τῷ Γ τὸ Α ὑπάρξει· τοῦτο

δ' ἦν ἀληθές.

Ἐπὶ δὲ τῶν ἐν μέρει συλλογισμῶν ἐνδέχεται καὶ τῆς

πρώτης προτάσεως ὅλης οὔσης ψευδοῦς τῆς δ' ἑτέρας ἀληθοῦς

ἀληθὲς εἶναι τὸ συμπέρασμα, καὶ ἐπί τι ψευδοῦς οὔσης τῆς

20 πρώτης τῆς δ' ἑτέρας ἀληθοῦς, καὶ τῆς μὲν ἀληθοῦς τῆς

δ' ἐν μέρει ψευδοῦς, καὶ ἀμφοτέρων ψευδῶν. οὐδὲν γὰρ κωλύει

τὸ Α τῷ μὲν Β μηδενὶ ὑπάρχειν τῷ δὲ Γ τινί, καὶ

τὸ Β τῷ Γ τινί, οἷον ζῷον οὐδεμιᾷ χιόνι λευκῷ δὲ τινὶ

ὑπάρχει, καὶ ἡ χιὼν λευκῷ τινί. εἰ οὖν μέσον τεθείη ἡ χιών,

25 πρῶτον δὲ τὸ ζῷον, καὶ ληφθείη τὸ μὲν Α ὅλῳ τῷ Β ὑπάρχειν,

τὸ δὲ Β τινὶ τῷ Γ, ἡ μὲν Α Β ὅλη ψευδής, ἡ δὲ

Β Γ ἀληθής, καὶ τὸ συμπέρασμα ἀληθές. ὁμοίως δὲ καὶ

στερητικῆς οὔσης τῆς Α Β προτάσεως· ἐγχωρεῖ γὰρ τὸ Α τῷ

μὲν Β ὅλῳ ὑπάρχειν τῷ δὲ Γ τινὶ μὴ ὑπάρχειν, τὸ μέντοι

30 Β τινὶ τῷ Γ ὑπάρχειν, οἷον τὸ ζῷον ἀνθρώπῳ μὲν παντὶ

ὑπάρχει, λευκῷ δὲ τινὶ οὐχ ἕπεται, ὁ δ' ἄνθρωπος τινὶ

λευκῷ ὑπάρχει, ὥστ' εἰ μέσου τεθέντος τοῦ ἀνθρώπου ληφθείη

τὸ Α μηδενὶ τῷ Β ὑπάρχειν, τὸ δὲ Β τινὶ τῷ Γ ὑπάρχειν,

ἀληθὲς ἔσται τὸ συμπέρασμα ψευδοῦς οὔσης ὅλης τῆς Α Β

35 προτάσεως. καὶ εἰ ἐπί τι ψευδὴς ἡ Α Β πρότασις, ἔσται τὸ

συμπέρασμα ἀληθές. οὐδὲν γὰρ κωλύει τὸ Α καὶ τῷ Β καὶ

τῷ Γ τινὶ ὑπάρχειν, καὶ τὸ Β τῷ Γ τινὶ ὑπάρχειν, οἷον τὸ

ζῷον τινὶ καλῷ καὶ τινὶ μεγάλῳ, καὶ τὸ καλὸν τινὶ μεγάλῳ

ὑπάρχειν. ἐὰν οὖν ληφθῇ τὸ Α παντὶ τῷ Β καὶ τὸ Β τινὶ τῷ Γ,

1If then it is assumed that A belongs to all B and B to all C, the conclusion will be true, although the premiss BC is wholly false. 10Similarly if the premiss AB is negative. For it is possible that A should belong neither to any B nor to any C, and that B should not belong to any C, e.g. a genus to species of another genus: for animal belongs neither to music nor to the art of healing, nor does music belong to the art of healing. If then it is assumed that A belongs to no B, and B to all C, the conclusion will be true.
(6) And if the premiss BC is not wholly false but in part only, even so the conclusion may be true. For nothing prevents A belonging 5to the whole of B and of C, while B belongs to some C, e.g. a genus to its species and difference: for animal belongs to every man and to every footed thing, and man to some footed things though not to all. If then it is assumed that A belongs to all B, and B to all C, A will belong to all C: and this ex hypothesi is true. Similarly if the premiss AB is negative. For it is possible that A should neither belong to any B nor to any C, though B belongs to some C, e.g. a genus to the species of another genus and its difference: for animal neither belongs to any wisdom nor to any instance of 'speculative', but wisdom belongs to some instance of 'speculative'. If then it should be assumed that A belongs to no B, 15and B to all C, will belong to no C: and this ex hypothesi is true.
In particular syllogisms it is possible when the first premiss is wholly false, and the other true, that the conclusion should be true; 20also when the first premiss is false in part, and the other true; and when the first is true, and the particular is false; and when both are false. (7) For nothing prevents A belonging to no B, but to some C, and B to some C, e.g. animal belongs to no snow, but to some white thing, and snow to some white thing. If then snow is taken as middle, 25and animal as first term, and it is assumed that A belongs to the whole of B, and B to some C, then the premiss BC is wholly false, the premiss BC true, and the conclusion true. Similarly if the premiss AB is negative: for it is possible that A should belong to the whole of B, but not to some C, 30although B belongs to some C, e.g. animal belongs to every man, but does not follow some white, but man belongs to some white; consequently if man be taken as middle term and it is assumed that A belongs to no B but B belongs to some C, the conclusion will be true although the premiss AB is wholly false. (35If the premiss AB is false in part, the conclusion may be true. For nothing prevents A belonging both to B and to some C, and B belonging to some C, e.g.

55a

1 ἡ μὲν Α Β πρότασις ἐπί τι ψευδὴς ἔσται, ἡ δὲ Β Γ ἀληθής,

καὶ τὸ συμπέρασμα ἀληθές. ὁμοίως δὲ καὶ στερητικῆς

οὔσης τῆς Α Β προτάσεως· οἱ γὰρ αὐτοὶ ὅροι ἔσονται καὶ

ὡσαύτως κείμενοι πρὸς τὴν ἀπόδειξιν. Πάλιν εἰ ἡ μὲν Α Β

5 ἀληθὴς ἡ δὲ Β Γ ψευδής, ἀληθὲς ἔσται τὸ συμπέρασμα.

οὐδὲν γὰρ κωλύει τὸ Α τῷ μὲν Β ὅλῳ ὑπάρχειν τῷ δὲ Γ

τινί, καὶ τὸ Β τῷ Γ μηδενὶ ὑπάρχειν, οἷον ζῷον κύκνῳ

μὲν παντὶ μέλανι δὲ τινί, κύκνος δὲ οὐδενὶ μέλανι. ὥστ' εἰ

ληφθείη παντὶ τῷ Β τὸ Α καὶ τὸ Β τινὶ τῷ Γ, ἀληθὲς

10 ἔσται τὸ συμπέρασμα ψευδοῦς ὄντος τοῦ Β Γ. ὁμοίως δὲ καὶ

στερητικῆς λαμβανομένης τῆς Α Β προτάσεως. ἐγχωρεῖ γὰρ

τὸ Α τῷ μὲν Β μηδενὶ τῷ δὲ Γ τινὶ μὴ ὑπάρχειν, τὸ

μέντοι Β μηδενὶ τῷ Γ, οἷον τὸ γένος τῷ ἐξ ἄλλου γένους

εἴδει καὶ τῷ συμβεβηκότι τοῖς αὑτοῦ εἴδεσι· τὸ γὰρ ζῷον

15 ἀριθμῷ μὲν οὐδενὶ ὑπάρχει λευκῷ δὲ τινί, ὁ δ' ἀριθμὸς

οὐδενὶ λευκῷ· ἐὰν οὖν μέσον τεθῇ ὁ ἀριθμός, καὶ ληφθῇ τὸ

μὲν Α μηδενὶ τῷ Β, τὸ δὲ Β τινὶ τῷ Γ, τὸ Α τινὶ τῷ Γ

οὐχ ὑπάρξει, ὅπερ ἦν ἀληθές· καὶ ἡ μὲν Α Β πρότασις

ἀληθής, ἡ δὲ Β Γ ψευδής. καὶ εἰ ἐπί τι ψευδὴς ἡ Α Β,

20 ψευδὴς δὲ καὶ ἡ Β Γ, ἔσται τὸ συμπέρασμα ἀληθές. οὐδὲν

γὰρ κωλύει τὸ Α τῷ Β τινὶ καὶ τῷ Γ τινὶ ὑπάρχειν ἑκατέρῳ,

τὸ δὲ Β μηδενὶ τῷ Γ, οἷον εἰ ἐναντίον τὸ Β τῷ Γ,

ἄμφω δὲ συμβεβηκότα τῷ αὐτῷ γένει· τὸ γὰρ ζῷον τινὶ

λευκῷ καὶ τινὶ μέλανι ὑπάρχει, λευκὸν δ' οὐδενὶ μέλανι.

25 ἐὰν οὖν ληφθῇ τὸ Α παντὶ τῷ Β καὶ τὸ Β τινὶ τῷ Γ,

ἀληθὲς ἔσται τὸ συμπέρασμα. καὶ στερητικῆς δὲ λαμβανομένης

τῆς Α Β ὡσαύτως· οἱ γὰρ αὐτοὶ ὅροι καὶ ὡσαύτως

τεθήσονται πρὸς τὴν ἀπόδειξιν. καὶ ἀμφοτέρων δὲ ψευδῶν

οὐσῶν ἔσται τὸ συμπέρασμα ἀληθές· ἐγχωρεῖ γὰρ τὸ Α τῷ

30 μὲν Β μηδενὶ τῷ δὲ Γ τινὶ ὑπάρχειν, τὸ μέντοι Β μηδενὶ

τῷ Γ, οἷον τὸ γένος τῷ ἐξ ἄλλου γένους εἴδει καὶ τῷ συμβεβηκότι

τοῖς εἴδεσι τοῖς αὑτοῦ· ζῷον γὰρ ἀριθμῷ μὲν

οὐδενὶ λευκῷ δὲ τινὶ ὑπάρχει, καὶ ὁ ἀριθμὸς οὐδενὶ λευκῷ.

ἐὰν οὖν ληφθῇ τὸ Α παντὶ τῷ Β καὶ τὸ Β τινὶ τῷ Γ, τὸ

35 μὲν συμπέρασμα ἀληθές, αἱ δὲ προτάσεις ἄμφω ψευδεῖς.

ὁμοίως δὲ καὶ στερητικῆς οὔσης τῆς Α Β. οὐδὲν γὰρ κωλύει

τὸ Α τῷ μὲν Β ὅλῳ ὑπάρχειν τῷ δὲ Γ τινὶ μὴ ὑπάρχειν,

μηδὲ τὸ Β μηδενὶ τῷ Γ, οἷον ζῷον κύκνῳ μὲν παντὶ

μέλανι δὲ τινὶ οὐχ ὑπάρχει, κύκνος δ' οὐδενὶ μέλανι. ὥστ' εἰ

40 ληφθείη τὸ Α μηδενὶ τῷ Β, τὸ δὲ Β τινὶ τῷ Γ, τὸ Α τινὶ

1animal to something beautiful and to something great, and beautiful belonging to something great. If then A is assumed to belong to all B, and B to some C, the a premiss AB will be partially false, the premiss BC will be true, and the conclusion true. Similarly if the premiss AB is negative. For the same terms will serve, and in the same positions, to prove the point.
(9) Again if 5the premiss AB is true, and the premiss BC is false, the conclusion may be true. For nothing prevents A belonging to the whole of B and to some C, while B belongs to no C, e.g. animal to every swan and to some black things, though swan belongs to no black thing. Consequently if it should be assumed that A belongs to all B, and B to some C, 10the conclusion will be true, although the statement Bc is false. Similarly if the premiss AB is negative. For it is possible that A should belong to no B, and not to some C, while B belongs to no C, e.g. a genus to the species of another genus and to the accident of its own species: 15for animal belongs to no number and not to some white things, and number belongs to nothing white. If then number is taken as middle, and it is assumed that A belongs to no B, and B to some C, then A will not belong to some C, which ex hypothesi is true. And the premiss AB is true, 20the premiss BC false.
(10) Also if the premiss AB is partially false, and the premiss BC is false too, the conclusion may be true. For nothing prevents A belonging to some B and to some C, though B belongs to no C, e.g. if B is the contrary of C, and both are accidents of the same genus: for animal belongs to some white things and to some black things, but white belongs to no black thing. 25If then it is assumed that A belongs to all B, and B to some C, the conclusion will be true. Similarly if the premiss AB is negative: for the same terms arranged in the same way will serve for the proof.
(11) Also though both premisses are false the conclusion may be true. For it is possible 30that A may belong to no B and to some C, while B belongs to no C, e.g. a genus in relation to the species of another genus, and to the accident of its own species: for animal belongs to no number, but to some white things, and number to nothing white. If then it is assumed that A belongs to all B and B to some C, 35the conclusion will be true, though both premisses are false. Similarly also if the premiss AB is negative. For nothing prevents A belonging to the whole of B, and not to some C, while B belongs to no C, e.g. 40animal belongs to every swan, and not to some black things, and swan belongs to nothing black.

55b

1 τῷ Γ οὐχ ὑπάρξει. τὸ μὲν οὖν συμπέρασμα ἀληθές, αἱ δὲ

προτάσεις ψευδεῖς.

1Consequently if it is assumed that A belongs to no B, and B to some C, then A does not belong to some C. The conclusion then is true, but the premisses arc false.

Book 2,Chapter 3 (55b3–56b3)

Ἐν δὲ τῷ μέσῳ σχήματι πάντως ἐγχωρεῖ διὰ ψευδῶν

ἀληθὲς συλλογίσασθαι, καὶ ἀμφοτέρων τῶν προτάσεων

5 ὅλων ψευδῶν λαμβανομένων καὶ ἐπί τι ἑκατέρας, καὶ τῆς

μὲν ἀληθοῦς τῆς δὲ ψευδοῦς οὔσης [ὅλης] ὁποτερασοῦν ψευδοῦς τιθεμένης,

[καὶ εἰ ἀμφότεραι ἐπί τι ψευδεῖς, καὶ εἰ ἡ μὲν ἁπλῶς

ἀληθὴς ἡ δ' ἐπί τι ψευδής, καὶ εἰ ἡ μὲν ὅλη ψευδὴς ἡ

δ' ἐπί τι ἀληθής,] καὶ ἐν τοῖς καθόλου καὶ ἐπὶ τῶν ἐν μέρει

10 συλλογισμῶν. εἰ γὰρ τὸ Α τῷ μὲν Β μηδενὶ ὑπάρχει τῷ

δὲ Γ παντί, οἷον ζῷον λίθῳ μὲν οὐδενὶ ἵππῳ δὲ παντί, ἐὰν

ἐναντίως τεθῶσιν αἱ προτάσεις καὶ ληφθῇ τὸ Α τῷ μὲν Β

παντὶ τῷ δὲ Γ μηδενί, ἐκ ψευδῶν ὅλων τῶν προτάσεων

ἀληθὲς ἔσται τὸ συμπέρασμα. ὁμοίως δὲ καὶ εἰ τῷ μὲν Β

15 παντὶ τῷ δὲ Γ μηδενὶ ὑπάρχει τὸ Α· ὁ γὰρ αὐτὸς ἔσται

συλλογισμός. Πάλιν εἰ ἡ μὲν ἑτέρα ὅλη ψευδὴς ἡ δ' ἑτέρα

ὅλη ἀληθής· οὐδὲν γὰρ κωλύει τὸ Α καὶ τῷ Β καὶ τῷ Γ

παντὶ ὑπάρχειν, τὸ μέντοι Β μηδενὶ τῷ Γ, οἷον τὸ γένος

τοῖς μὴ ὑπ' ἄλληλα εἴδεσιν. τὸ γὰρ ζῷον καὶ ἵππῳ παντὶ

20 καὶ ἀνθρώπῳ, καὶ οὐδεὶς ἄνθρωπος ἵππος. ἐὰν οὖν ληφθῇ

τῷ μὲν παντὶ τῷ δὲ μηδενὶ ὑπάρχειν, ἡ μὲν ὅλη ψευδὴς

ἔσται ἡ δ' ὅλη ἀληθής, καὶ τὸ συμπέρασμα ἀληθὲς

πρὸς ὁποτερῳοῦν τεθέντος τοῦ στερητικοῦ. καὶ εἰ ἡ ἑτέρα ἐπί τι

ψευδής, ἡ δ' ἑτέρα ὅλη ἀληθής. ἐγχωρεῖ γὰρ τὸ Α τῷ

25 μὲν Β τινὶ ὑπάρχειν τῷ δὲ Γ παντί, τὸ μέντοι Β μηδενὶ

τῷ Γ, οἷον ζῷον λευκῷ μὲν τινὶ κόρακι δὲ παντί, καὶ τὸ

λευκὸν οὐδενὶ κόρακι. ἐὰν οὖν ληφθῇ τὸ Α τῷ μὲν Β μηδενὶ

τῷ δὲ Γ ὅλῳ ὑπάρχειν, ἡ μὲν Α Β πρότασις ἐπί τι ψευδής,

ἡ δ' Α Γ ὅλη ἀληθής, καὶ τὸ συμπέρασμα ἀληθές.

30 καὶ μετατιθεμένου δὲ τοῦ στερητικοῦ ὡσαύτως· διὰ γὰρ τῶν

αὐτῶν ὅρων ἡ ἀπόδειξις. καὶ εἰ ἡ καταφατικὴ πρότασις ἐπί

τι ψευδής, ἡ δὲ στερητικὴ ὅλη ἀληθής. οὐδὲν γὰρ κωλύει τὸ

Α τῷ μὲν Β τινὶ ὑπάρχειν τῷ δὲ Γ ὅλῳ μὴ ὑπάρχειν,

καὶ τὸ Β μηδενὶ τῷ Γ, οἷον τὸ ζῷον λευκῷ μὲν τινὶ πίττῃ

35 δ' οὐδεμιᾷ, καὶ τὸ λευκὸν οὐδεμιᾷ πίττῃ. ὥστ' ἐὰν ληφθῇ τὸ

Α ὅλῳ τῷ Β ὑπάρχειν τῷ δὲ Γ μηδενί, ἡ μὲν Α Β ἐπί τι

ψευδής, ἡ δ' Α Γ ὅλη ἀληθής, καὶ τὸ συμπέρασμα ἀληθές.

καὶ εἰ ἀμφότεραι αἱ προτάσεις ἐπί τι ψευδεῖς, ἔσται

τὸ συμπέρασμα ἀληθές. ἐγχωρεῖ γὰρ τὸ Α καὶ τῷ Β καὶ

40 τῷ Γ τινὶ ὑπάρχειν, τὸ δὲ Β μηδενὶ τῷ Γ, οἷον ζῷον καὶ

3In the middle figure it is possible in every way to reach a true conclusion through false premisses, whether the syllogisms are universal or particular, viz. when both premisses are wholly false; when each is partially false; 5when one is true, the other wholly false (it does not matter which of the two premisses is false); if both premisses are partially false; if one is quite true, the other partially false; if one is wholly false, the other partially true. For (1) 10if A belongs to no B and to all C, e.g. animal to no stone and to every horse, then if the premisses are stated contrariwise and it is assumed that A belongs to all B and to no C, though the premisses are wholly false they will yield a true conclusion. Similarly if A belongs to all B 15and to no C: for we shall have the same syllogism.
(2) Again if one premiss is wholly false, the other wholly true: for nothing prevents A belonging to all B and to all C, though B belongs to no C, e.g. a genus to its co-ordinate species. For animal belongs to every horse 20and man, and no man is a horse. If then it is assumed that animal belongs to all of the one, and none of the other, the one premiss will be wholly false, the other wholly true, and the conclusion will be true whichever term the negative statement concerns.
(3) Also if one premiss is partially false, the other wholly true. For it is possible that A should 25belong to some B and to all C, though B belongs to no C, e.g. animal to some white things and to every raven, though white belongs to no raven. If then it is assumed that A belongs to no B, but to the whole of C, the premiss AB is partially false, the premiss AC wholly true, and the conclusion true. 30Similarly if the negative statement is transposed: the proof can be made by means of the same terms. Also if the affirmative premiss is partially false, the negative wholly true, a true conclusion is possible. For nothing prevents A belonging to some B, but not to C as a whole, while B belongs to no C, e.g. animal belongs to some white things, but to no pitch, 35and white belongs to no pitch. Consequently if it is assumed that A belongs to the whole of B, but to no C, the premiss AB is partially false, the premiss AC is wholly true, and the conclusion is true.
(4) And if both the premisses are partially false, the conclusion may be true. For it is possible that A should belong to some B 40and to some C, and B to no C, e.g.

56a

1 λευκῷ τινὶ καὶ μέλανί τινι, τὸ δὲ λευκὸν οὐδενὶ μέλανι. ἐὰν οὖν

ληφθῇ τὸ Α τῷ μὲν Β παντὶ τῷ δὲ Γ μηδενί, ἄμφω μὲν αἱ

προτάσεις ἐπί τι ψευδεῖς, τὸ δὲ συμπέρασμα ἀληθές. ὁμοίως

δὲ καὶ μετατεθείσης τῆς στερητικῆς διὰ τῶν αὐτῶν ὅρων.

5 Φανερὸν δὲ καὶ ἐπὶ τῶν ἐν μέρει συλλογισμῶν· οὐδὲν

γὰρ κωλύει τὸ Α τῷ μὲν Β παντὶ τῷ δὲ Γ τινὶ ὑπάρχειν,

καὶ τὸ Β τῷ Γ τινὶ μὴ ὑπάρχειν, οἷον ζῷον παντὶ ἀνθρώπῳ

λευκῷ δὲ τινί, ἄνθρωπος δὲ τινὶ λευκῷ οὐχ ὑπάρξει.

ἐὰν οὖν τεθῇ τὸ Α τῷ μὲν Β μηδενὶ ὑπάρχειν τῷ δὲ Γ τινὶ

10 ὑπάρχειν, ἡ μὲν καθόλου πρότασις ὅλη ψευδής, ἡ δ' ἐν μέρει

ἀληθής, καὶ τὸ συμπέρασμα ἀληθές. ὡσαύτως δὲ καὶ

καταφατικῆς λαμβανομένης τῆς Α Β· ἐγχωρεῖ γὰρ τὸ Α

τῷ μὲν Β μηδενὶ τῷ δὲ Γ τινὶ μὴ ὑπάρχειν, καὶ τὸ Β τῷ

Γ τινὶ μὴ ὑπάρχειν, οἷον τὸ ζῷον οὐδενὶ ἀψύχῳ, λευκῷ

15 δὲ τινί, καὶ τὸ ἄψυχον οὐχ ὑπάρξει τινὶ λευκῷ.

ἐὰν οὖν τεθῇ τὸ Α τῷ μὲν Β παντὶ τῷ δὲ Γ τινὶ μὴ ὑπάρχειν,

ἡ μὲν Α Β πρότασις, ἡ καθόλου, ὅλη ψευδής, ἡ δὲ

Α Γ ἀληθής, καὶ τὸ συμπέρασμα ἀληθές. καὶ τῆς μὲν καθόλου

ἀληθοῦς τεθείσης, τῆς δ' ἐν μέρει ψευδοῦς. οὐδὲν γὰρ

20 κωλύει τὸ Α μήτε τῷ Β μήτε τῷ Γ μηδενὶ ἕπεσθαι, τὸ μέντοι

Β τινὶ τῷ Γ μὴ ὑπάρχειν, οἷον ζῷον οὐδενὶ ἀριθμῷ οὐδ'

ἀψύχῳ, καὶ ὁ ἀριθμὸς τινὶ ἀψύχῳ οὐχ ἕπεται. ἐὰν οὖν τεθῇ

τὸ Α τῷ μὲν Β μηδενὶ τῷ δὲ Γ τινί, τὸ μὲν συμπέρασμα

ἔσται ἀληθὲς καὶ ἡ καθόλου πρότασις, ἡ δ' ἐν μέρει

25 ψευδής. καὶ καταφατικῆς δὲ τῆς καθόλου τιθεμένης ὡσαύτως.

ἐγχωρεῖ γὰρ τὸ Α καὶ τῷ Β καὶ τῷ Γ ὅλῳ ὑπάρχειν,

τὸ μέντοι Β τινὶ τῷ Γ μὴ ἕπεσθαι, οἷον τὸ γένος τῷ εἴδει

καὶ τῇ διαφορᾷ· τὸ γὰρ ζῷον παντὶ ἀνθρώπῳ καὶ ὅλῳ πεζῷ

ἕπεται, ἄνθρωπος δ' οὐ παντὶ πεζῷ. ὥστ' ἂν ληφθῇ τὸ Α τῷ

30 μὲν Β ὅλῳ ὑπάρχειν, τῷ δὲ Γ τινὶ μὴ ὑπάρχειν, ἡ μὲν καθόλου

πρότασις ἀληθής, ἡ δ' ἐν μέρει ψευδής, τὸ δὲ συμπέρασμα

ἀληθές. Φανερὸν δὲ καὶ ὅτι ἐξ ἀμφοτέρων ψευδῶν

ἔσται τὸ συμπέρασμα ἀληθές, εἴπερ ἐνδέχεται τὸ Α καὶ

τῷ Β καὶ τῷ Γ ὅλῳ ὑπάρχειν, τὸ μέντοι Β τινὶ τῷ Γ μὴ

35 ἕπεσθαι. ληφθέντος γὰρ τοῦ Α τῷ μὲν Β μηδενὶ τῷ δὲ Γ τινὶ

ὑπάρχειν, αἱ μὲν προτάσεις ἀμφότεραι ψευδεῖς, τὸ δὲ

συμπέρασμα ἀληθές. ὁμοίως δὲ καὶ κατηγορικῆς οὔσης τῆς

καθόλου προτάσεως, τῆς δ' ἐν μέρει στερητικῆς. ἐγχωρεῖ γὰρ

τὸ Α τῷ μὲν Β μηδενὶ τῷ δὲ Γ παντὶ ἕπεσθαι, καὶ τὸ Β

40 τινὶ τῷ Γ μὴ ὑπάρχειν, οἷον ζῷον ἐπιστήμῃ μὲν οὐδεμιᾷ ἀνθρώπῳ

δὲ παντὶ ἕπεται, ἡ δ' ἐπιστήμη οὐ παντὶ ἀνθρώπῳ.

1animal to some white things and to some black things, though white belongs to nothing black. If then it is assumed that A belongs to all B and to no C, both premisses are partially false, but the conclusion is true. Similarly, if the negative premiss is transposed, the proof can be made by means of the same terms.
5It is clear also that our thesis holds in particular syllogisms. For (5) nothing prevents A belonging to all B and to some C, 40though B does not belong to some C, e.g. animal to every man and to some white things, though man will not belong to some white things. If then it is stated that A belongs to no B and to some C, 10the universal premiss is wholly false, the particular premiss is true, and the conclusion is true. Similarly if the premiss AB is affirmative: for it is possible that A should belong to no B, and not to some C, though B does not belong to some C, e.g. animal belongs to nothing lifeless, and does not belong to some white things, 15and lifeless will not belong to some white things. If then it is stated that A belongs to all B and not to some C, the premiss AB which is universal is wholly false, the premiss AC is true, and the conclusion is true. Also a true conclusion is possible when the universal premiss is true, and the particular is false. For nothing prevents 20A following neither B nor C at all, while B does not belong to some C, e.g. animal belongs to no number nor to anything lifeless, and number does not follow some lifeless things. If then it is stated that A belongs to no B and to some C, the conclusion will be true, and the universal premiss true, but the particular 25false. Similarly if the premiss which is stated universally is affirmative. For it is possible that should A belong both to B and to C as wholes, though B does not follow some C, e.g. a genus in relation to its species and difference: for animal follows every man and footed things as a whole, but man does not follow every footed thing. Consequently if it is assumed that A belongs 30to the whole of B, but does not belong to some C, the universal premiss is true, the particular false, and the conclusion true.
(6) It is clear too that though both premisses are false they may yield a true conclusion, since it is possible that A should belong both to B and to C as wholes, though B does not follow some C. 35For if it is assumed that A belongs to no B and to some C, the premisses are both false, but the conclusion is true. Similarly if the universal premiss is affirmative and the particular negative. For it is possible that A should follow no B and all C, though B does not belong to some C, e.g.

56b

1 ἐὰν οὖν ληφθῇ τὸ Α τῷ μὲν Β ὅλῳ ὑπάρχειν, τῷ δὲ Γ τινὶ

μὴ ἕπεσθαι, αἱ μὲν προτάσεις ψευδεῖς, τὸ δὲ συμπέρασμα

ἀληθές.

1animal follows no science but every man, though science does not follow every man. If then A is assumed to belong to the whole of B, and not to follow some C, the premisses are false but the conclusion is true.

Book 2,Chapter 4 (56b4–57b17)

Ἔσται δὲ καὶ ἐν τῷ ἐσχάτῳ σχήματι διὰ ψευδῶν

5 ἀληθές, καὶ ἀμφοτέρων ψευδῶν οὐσῶν ὅλων καὶ ἐπί τι ἑκατέρας,

καὶ τῆς μὲν ἑτέρας ἀληθοῦς ὅλης τῆς δ' ἑτέρας ψευδοῦς,

καὶ τῆς μὲν ἐπί τι ψευδοῦς τῆς δ' ὅλης ἀληθοῦς, καὶ ἀνάπαλιν,

καὶ ὁσαχῶς ἄλλως ἐγχωρεῖ μεταλαβεῖν τὰς προτάσεις.

οὐδὲν γὰρ κωλύει μήτε τὸ Α μήτε τὸ Β μηδενὶ τῷ

10 Γ ὑπάρχειν, τὸ μέντοι Α τινὶ τῷ Β ὑπάρχειν, οἷον οὔτ' ἄνθρωπος

οὔτε πεζὸν οὐδενὶ ἀψύχῳ ἕπεται, ἄνθρωπος μέντοι τινὶ

πεζῷ ὑπάρχει. ἐὰν οὖν ληφθῇ τὸ Α καὶ τὸ Β παντὶ τῷ Γ

ὑπάρχειν, αἱ μὲν προτάσεις ὅλαι ψευδεῖς, τὸ δὲ συμπέρασμα

ἀληθές. ὡσαύτως δὲ καὶ τῆς μὲν στερητικῆς τῆς δὲ καταφατικῆς

15 οὔσης. ἐγχωρεῖ γὰρ τὸ μὲν Β μηδενὶ τῷ Γ ὑπάρχειν,

τὸ δὲ Α παντί, καὶ τὸ Α τινὶ τῷ Β μὴ ὑπάρχειν,

οἷον τὸ μέλαν οὐδενὶ κύκνῳ, ζῷον δὲ παντί, καὶ τὸ ζῷον οὐ

παντὶ μέλανι. ὥστ' ἂν ληφθῇ τὸ μὲν Β παντὶ τῷ Γ, τὸ δὲ

Α μηδενί, τὸ Α τινὶ τῷ Β οὐχ ὑπάρξει· καὶ τὸ μὲν συμπέρασμα

20 ἀληθές, αἱ δὲ προτάσεις ψευδεῖς. καὶ εἰ ἐπί τι

ἑκατέρα ψευδής, ἔσται τὸ συμπέρασμα ἀληθές. οὐδὲν γὰρ

κωλύει καὶ τὸ Α καὶ τὸ Β τινὶ τῷ Γ ὑπάρχειν, καὶ τὸ

Α τινὶ τῷ Β, οἷον τὸ λευκὸν καὶ τὸ καλὸν τινὶ ζῴῳ ὑπάρχει,

καὶ τὸ λευκὸν τινὶ καλῷ. ἐὰν οὖν τεθῇ τὸ Α καὶ τὸ

25 Β παντὶ τῷ Γ ὑπάρχειν, αἱ μὲν προτάσεις ἐπί τι ψευδεῖς,

τὸ δὲ συμπέρασμα ἀληθές. καὶ στερητικῆς δὲ τῆς Α Γ τιθεμένης

ὁμοίως. οὐδὲν γὰρ κωλύει τὸ μὲν Α τινὶ τῷ Γ μὴ

ὑπάρχειν, τὸ δὲ Β τινὶ ὑπάρχειν, καὶ τὸ Α τῷ Β μὴ παντὶ

ὑπάρχειν, οἷον τὸ λευκὸν τινὶ ζῴῳ οὐχ ὑπάρχει, τὸ δὲ καλὸν

30 τινὶ ὑπάρχει, καὶ τὸ λευκὸν οὐ παντὶ καλῷ. ὥστ' ἂν

ληφθῇ τὸ μὲν Α μηδενὶ τῷ Γ, τὸ δὲ Β παντί, ἀμφότεραι

μὲν αἱ προτάσεις ἐπί τι ψευδεῖς, τὸ δὲ συμπέρασμα ἀληθές.

Ὡσαύτως δὲ καὶ τῆς μὲν ὅλης ψευδοῦς τῆς δ' ὅλης

ἀληθοῦς λαμβανομένης. ἐγχωρεῖ γὰρ καὶ τὸ Α καὶ τὸ Β

35 παντὶ τῷ Γ ἕπεσθαι, τὸ μέντοι Α τινὶ τῷ Β μὴ ὑπάρχειν,

οἷον ζῷον καὶ λευκὸν παντὶ κύκνῳ ἕπεται, τὸ μέντοι ζῷον

οὐ παντὶ ὑπάρχει λευκῷ. τεθέντων οὖν ὅρων τοιούτων, ἐὰν ληφθῇ

τὸ μὲν Β ὅλῳ τῷ Γ ὑπάρχειν, τὸ δὲ Α ὅλῳ μὴ ὑπάρχειν,

ἡ μὲν Β Γ ὅλη ἔσται ἀληθής, ἡ δὲ Α Γ ὅλη ψευδής, καὶ

40 τὸ συμπέρασμα ἀληθές. ὁμοίως δὲ καὶ εἰ τὸ μὲν Β Γ ψεῦδος,

τὸ δὲ Α Γ ἀληθές· οἱ γὰρ αὐτοὶ ὅροι πρὸς τὴν ἀπόδειξιν

4In the last figure a true conclusion may come through what is false, 5alike when both premisses are wholly false, when each is partly false, when one premiss is wholly true, the other false, when one premiss is partly false, the other wholly true, and vice versa, and in every other way in which it is possible to alter the premisses. For (1) nothing prevents neither A nor B from belonging to any C, 10while A belongs to some B, e.g. neither man nor footed follows anything lifeless, though man belongs to some footed things. If then it is assumed that A and B belong to all C, the premisses will be wholly false, but the conclusion true. Similarly if one premiss is negative, the other affirmative. 15For it is possible that B should belong to no C, but A to all C, and that should not belong to some B, e.g. black belongs to no swan, animal to every swan, and animal not to everything black. Consequently if it is assumed that B belongs to all C, and A to no C, A will not belong to some B: and 20the conclusion is true, though the premisses are false.
(2) Also if each premiss is partly false, the conclusion may be true. For nothing prevents both A and B from belonging to some C while A belongs to some B, e.g. white and beautiful belong to some animals, and white to some beautiful things. If then it is stated that A and B 25belong to all C, the premisses are partially false, but the conclusion is true. Similarly if the premiss AC is stated as negative. For nothing prevents A from not belonging, and B from belonging, to some C, while A does not belong to all B, e.g. white does not belong to some animals, 30beautiful belongs to some animals, and white does not belong to everything beautiful. Consequently if it is assumed that A belongs to no C, and B to all C, both premisses are partly false, but the conclusion is true.
(3) Similarly if one of the premisses assumed is wholly false, the other wholly true. For it is possible that both A and B 35should follow all C, though A does not belong to some B, e.g. animal and white follow every swan, though animal does not belong to everything white. Taking these then as terms, if one assumes that B belongs to the whole of C, but A does not belong to C at all, the premiss BC will be wholly true, the premiss AC wholly false, 40and the conclusion true. Similarly if the statement BC is false, the statement AC true, the conclusion may be true. The same terms will serve for the proof. Also if both the premisses assumed are affirmative, the conclusion may be true. For nothing prevents B from following all C, and A from not belonging to C at all, though A belongs to some B, e.g.

57a

1 [μέλαν—κύκνος—ἄψυχον]. ἀλλὰ καὶ εἰ ἀμφότεραι

λαμβάνοιντο καταφατικαί. οὐδὲν γὰρ κωλύει τὸ μὲν Β

παντὶ τῷ Γ ἕπεσθαι, τὸ δὲ Α ὅλῳ μὴ ὑπάρχειν, καὶ τὸ

Α τινὶ τῷ Β ὑπάρχειν, οἷον κύκνῳ παντὶ ζῷον, μέλαν

5 δ' οὐδενὶ κύκνῳ, καὶ τὸ μέλαν ὑπάρχει τινὶ ζῴῳ. ὥστ' ἂν

ληφθῇ τὸ Α καὶ τὸ Β παντὶ τῷ Γ ὑπάρχειν, ἡ μὲν Β Γ

ὅλη ἀληθής, ἡ δὲ Α Γ ὅλη ψευδής, καὶ τὸ συμπέρασμα

ἀληθές. ὁμοίως δὲ καὶ τῆς Α Γ ληφθείσης ἀληθοῦς· διὰ

γὰρ τῶν αὐτῶν ὅρων ἡ ἀπόδειξις. Πάλιν τῆς μὲν ὅλης ἀληθοῦς

10 οὔσης, τῆς δ' ἐπί τι ψευδοῦς. ἐγχωρεῖ γὰρ τὸ μὲν Β

παντὶ τῷ Γ ὑπάρχειν, τὸ δὲ Α τινί, καὶ τὸ Α τινὶ τῷ Β,

οἷον δίπουν μὲν παντὶ ἀνθρώπῳ, καλὸν δ' οὐ παντί, καὶ τὸ

καλὸν τινὶ δίποδι ὑπάρχει. ἐὰν οὖν ληφθῇ καὶ τὸ Α καὶ

τὸ Β ὅλῳ τῷ Γ ὑπάρχειν, ἡ μὲν Β Γ ὅλη ἀληθής, ἡ δὲ

15 Α Γ ἐπί τι ψευδής, τὸ δὲ συμπέρασμα ἀληθές. ὁμοίως δὲ

καὶ τῆς μὲν Α Γ ἀληθοῦς τῆς δὲ Β Γ ἐπί τι ψευδοῦς λαμβανομένης·

μετατεθέντων γὰρ τῶν αὐτῶν ὅρων ἔσται ἡ ἀπόδειξις.

καὶ τῆς μὲν στερητικῆς τῆς δὲ καταφατικῆς οὔσης.

ἐπεὶ γὰρ ἐγχωρεῖ τὸ μὲν Β ὅλῳ τῷ Γ ὑπάρχειν, τὸ δὲ Α

20 τινί, καὶ ὅταν οὕτως ἔχωσιν, οὐ παντὶ τῷ Β τὸ Α, ἐὰν οὖν ληφθῇ

τὸ μὲν Β ὅλῳ τῷ Γ ὑπάρχειν, τὸ δὲ Α μηδενί, ἡ

μὲν στερητικὴ ἐπί τι ψευδής, ἡ δ' ἑτέρα ὅλη ἀληθὴς καὶ τὸ

συμπέρασμα. πάλιν ἐπεὶ δέδεικται ὅτι τοῦ μὲν Α μηδενὶ

ὑπάρχοντος τῷ Γ, τοῦ δὲ Β τινί, ἐγχωρεῖ τὸ Α τινὶ τῷ Β

25 μὴ ὑπάρχειν, φανερὸν ὅτι καὶ τῆς μὲν Α Γ ὅλης ἀληθοῦς

οὔσης, τῆς δὲ Β Γ ἐπί τι ψευδοῦς, ἐγχωρεῖ τὸ συμπέρασμα

εἶναι ἀληθές. ἐὰν γὰρ ληφθῇ τὸ μὲν Α μηδενὶ τῷ Γ, τὸ δὲ

Β παντί, ἡ μὲν Α Γ ὅλη ἀληθής, ἡ δὲ Β Γ ἐπί τι ψευδής.

Φανερὸν δὲ καὶ ἐπὶ τῶν ἐν μέρει συλλογισμῶν ὅτι πάντως

30 ἔσται διὰ ψευδῶν ἀληθές. οἱ γὰρ αὐτοὶ ὅροι ληπτέοι

καὶ ὅταν καθόλου ὦσιν αἱ προτάσεις, οἱ μὲν ἐν τοῖς κατηγορικοῖς

κατηγορικοί, οἱ δ' ἐν τοῖς στερητικοῖς στερητικοί.

οὐδὲν γὰρ διαφέρει μηδενὶ ὑπάρχοντος παντὶ λαβεῖν ὑπάρχειν,

καὶ τινὶ ὑπάρχοντος καθόλου λαβεῖν ὑπάρχειν, πρὸς

35 τὴν τῶν ὅρων ἔκθεσιν· ὁμοίως δὲ καὶ ἐπὶ τῶν στερητικῶν.

Φανερὸν οὖν ὅτι ἂν μὲν ᾖ τὸ συμπέρασμα ψεῦδος,

ἀνάγκη, ἐξ ὧν ὁ λόγος, ψευδῆ εἶναι ἢ πάντα ἢ ἔνια, ὅταν

δ' ἀληθές, οὐκ ἀνάγκη ἀληθὲς εἶναι οὔτε τὶ οὔτε πάντα, ἀλλ'

ἔστι μηδενὸς ὄντος ἀληθοῦς τῶν ἐν τῷ συλλογισμῷ τὸ συμπέρασμα

40 ὁμοίως εἶναι ἀληθές· οὐ μὴν ἐξ ἀνάγκης. αἴτιον δ'

1animal belongs to every swan, 5black to no swan, and black to some animals. Consequently if it is assumed that A and B belong to every C, the premiss BC is wholly true, the premiss AC is wholly false, and the conclusion is true. Similarly if the premiss AC which is assumed is true: the proof can be made through the same terms.
(4) Again if one premiss is wholly true, 10the other partly false, the conclusion may be true. For it is possible that B should belong to all C, and A to some C, while A belongs to some B, e.g. biped belongs to every man, beautiful not to every man, and beautiful to some bipeds. If then it is assumed that both A and B belong to the whole of C, the premiss BC is wholly true, 15the premiss AC partly false, the conclusion true. Similarly if of the premisses assumed AC is true and BC partly false, a true conclusion is possible: this can be proved, if the same terms as before are transposed. Also the conclusion may be true if one premiss is negative, the other affirmative. For since it is possible that B should belong to the whole of C, 20and A to some C, and, when they are so, that A should not belong to all B, therefore it is assumed that B belongs to the whole of C, and A to no C, the negative premiss is partly false, the other premiss wholly true, and the conclusion is true. Again since it has been proved that if A belongs to no C and B to some C, it is possible that A should not belong to some C, 25it is clear that if the premiss AC is wholly true, and the premiss BC partly false, it is possible that the conclusion should be true. For if it is assumed that A belongs to no C, and B to all C, the premiss AC is wholly true, and the premiss BC is partly false.
(5) It is clear also in the case of particular syllogisms that 30a true conclusion may come through what is false, in every possible way. For the same terms must be taken as have been taken when the premisses are universal, positive terms in positive syllogisms, negative terms in negative. For it makes no difference to the setting out of the terms, whether one assumes that what belongs to none belongs to all or that what belongs to some belongs to all. 35The same applies to negative statements.
It is clear then that if the conclusion is false, the premisses of the argument must be false, either all or some of them; but when the conclusion is true, it is not necessary that the premisses should be true, either one or all, yet it is possible, though no part of the syllogism is true, that 40the conclusion may none the less be true; but it is not necessitated.

57b

1 ὅτι ὅταν δύο ἔχῃ οὕτω πρὸς ἄλληλα ὥστε θατέρου ὄντος ἐξ

ἀνάγκης εἶναι θάτερον, τούτου μὴ ὄντος μὲν οὐδὲ θάτερον ἔσται,

ὄντος δ' οὐκ ἀνάγκη εἶναι θάτερον· τοῦ δ' αὐτοῦ ὄντος καὶ μὴ

ὄντος ἀδύνατον ἐξ ἀνάγκης εἶναι τὸ αὐτό· λέγω δ' οἷον τοῦ

5 Α ὄντος λευκοῦ τὸ Β εἶναι μέγα ἐξ ἀνάγκης, καὶ μὴ ὄντος

λευκοῦ τοῦ Α τὸ Β εἶναι μέγα ἐξ ἀνάγκης. ὅταν γὰρ τουδὶ ὄντος

λευκοῦ, τοῦ Α, τοδὶ ἀνάγκη μέγα εἶναι, τὸ Β, μεγάλου

δὲ τοῦ Β ὄντος τὸ Γ μὴ λευκόν, ἀνάγκη, εἰ τὸ Α λευκόν,

τὸ Γ μὴ εἶναι λευκόν. καὶ ὅταν δύο ὄντων θατέρου ὄντος

10 ἀνάγκη θάτερον εἶναι, τούτου μὴ ὄντος ἀνάγκη τὸ πρῶτον μὴ

εἶναι. τοῦ δὴ Β μὴ ὄντος μεγάλου τὸ Α οὐχ οἷόν τε λευκὸν

εἶναι. τοῦ δὲ Α μὴ ὄντος λευκοῦ εἰ ἀνάγκη τὸ Β μέγα εἶναι,

συμβαίνει ἐξ ἀνάγκης τοῦ Β μεγάλου μὴ ὄντος αὐτὸ τὸ Β

εἶναι μέγα· τοῦτο δ' ἀδύνατον. εἰ γὰρ τὸ Β μὴ ἔστι μέγα,

15 τὸ Α οὐκ ἔσται λευκὸν ἐξ ἀνάγκης. εἰ οὖν μὴ ὄντος τούτου λευκοῦ

τὸ Β ἔσται μέγα, συμβαίνει, εἰ τὸ Β μὴ ἔστι μέγα,

εἶναι μέγα, ὡς διὰ τριῶν.

1The reason is that when two things are so related to one another, that if the one is, the other necessarily is, then if the latter is not, the former will not be either, but if the latter is, it is not necessary that the former should be. But it is impossible that the same thing should be necessitated by the being and by the not-being of the same thing. I mean, for example, that it is impossible 5that B should necessarily be great since A is white and that B should necessarily be great since A is not white. For whenever since this, A, is white it is necessary that that, B, should be great, and since B is great that C should not be white, then it is necessary if is white that C should not be white. And whenever it is necessary, since one of two things is, 10that the other should be, it is necessary, if the latter is not, that the former (viz. A) should not be. If then B is not great A cannot be white. But if, when A is not white, it is necessary that B should be great, it necessarily results that if B is not great, B itself is great. (But this is impossible.) For if B is not great, 15A will necessarily not be white. If then when this is not white B must be great, it results that if B is not great, it is great, just as if it were proved through three terms.

Book 2,Chapter 5 (57b18–58b12)

Τὸ δὲ κύκλῳ καὶ ἐξ ἀλλήλων δείκνυσθαί ἐστι τὸ διὰ

τοῦ συμπεράσματος καὶ τοῦ ἀνάπαλιν τῇ κατηγορίᾳ τὴν

20 ἑτέραν λαβόντα πρότασιν συμπεράνασθαι τὴν λοιπήν, ἣν

ἐλάμβανεν ἐν θατέρῳ συλλογισμῷ. οἷον εἰ ἔδει δεῖξαι ὅτι

τὸ Α τῷ Γ παντὶ ὑπάρχει, ἔδειξε δὲ διὰ τοῦ Β, πάλιν εἰ

δεικνύοι ὅτι τὸ Α τῷ Β ὑπάρχει, λαβὼν τὸ μὲν Α τῷ Γ

ὑπάρχειν τὸ δὲ Γ τῷ Β [καὶ τὸ Α τῷ Β]· πρότερον δ' ἀνάπαλιν

25 ἔλαβε τὸ Β τῷ Γ ὑπάρχον. ἢ εἰ [ὅτι] τὸ Β τῷ Γ δεῖ

δεῖξαι ὑπάρχον, εἰ λάβοι τὸ Α κατὰ τοῦ Γ, ὃ ἦν συμπέρασμα,

τὸ δὲ Β κατὰ τοῦ Α ὑπάρχειν· πρότερον δ' ἐλήφθη

ἀνάπαλιν τὸ Α κατὰ τοῦ Β. ἄλλως δ' οὐκ ἔστιν ἐξ ἀλλήλων

δεῖξαι. εἴτε γὰρ ἄλλο μέσον λήψεται, οὐ κύκλῳ·

30 οὐδὲν γὰρ λαμβάνεται τῶν αὐτῶν· εἴτε τούτων τι, ἀνάγκη

θάτερον μόνον· εἰ γὰρ ἄμφω, ταὐτὸν ἔσται συμπέρασμα,

δεῖ δ' ἕτερον. Ἐν μὲν οὖν τοῖς μὴ ἀντιστρέφουσιν ἐξ ἀναποδείκτου

τῆς ἑτέρας προτάσεως γίνεται ὁ συλλογισμός· οὐ γὰρ

ἔστιν ἀποδεῖξαι διὰ τούτων τῶν ὅρων ὅτι τῷ μέσῳ τὸ τρίτον

35 ὑπάρχει ἢ τῷ πρώτῳ τὸ μέσον. ἐν δὲ τοῖς ἀντιστρέφουσιν

ἔστι πάντα δεικνύναι δι' ἀλλήλων, οἷον εἰ τὸ Α καὶ τὸ Β

καὶ τὸ Γ ἀντιστρέφουσιν ἀλλήλοις. δεδείχθω γὰρ τὸ Α Γ

διὰ μέσου τοῦ Β, καὶ πάλιν τὸ Α Β διά τε τοῦ συμπεράσματος

καὶ διὰ τῆς Β Γ προτάσεως ἀντιστραφείσης, ὡσαύτως

40 δὲ καὶ τὸ Β Γ διά τε τοῦ συμπεράσματος καὶ τῆς Α Β

18Circular and reciprocal proof means proof by means of the conclusion, i.e. by converting one of the premisses simply 20and inferring the premiss which was assumed in the original syllogism: e.g. suppose it has been necessary to prove that A belongs to all C, and it has been proved through B; suppose that A should now be proved to belong to B by assuming that A belongs to C, and C to B-so A belongs to B: but in the first syllogism the converse was assumed, 25viz. that B belongs to C. Or suppose it is necessary to prove that B belongs to C, and A is assumed to belong to C, which was the conclusion of the first syllogism, and B to belong to A but the converse was assumed in the earlier syllogism, viz. that A belongs to B. In no other way is reciprocal proof possible. If another term is taken as middle, the proof is not circular: 30for neither of the propositions assumed is the same as before: if one of the accepted terms is taken as middle, only one of the premisses of the first syllogism can be assumed in the second: for if both of them are taken the same conclusion as before will result: but it must be different. If the terms are not convertible, one of the premisses from which the syllogism results must be undemonstrated: for it is not possible to demonstrate through these terms that the third belongs to the middle 35or the middle to the first. If the terms are convertible, it is possible to demonstrate everything reciprocally, e.g. 40if A and B and C are convertible with one another.

58a

1 προτάσεως ἀντεστραμμένης. δεῖ δὲ τήν τε Γ Β καὶ τὴν Β Α

πρότασιν ἀποδεῖξαι· ταύταις γὰρ ἀναποδείκτοις κεχρήμεθα

μόναις. ἐὰν οὖν ληφθῇ τὸ Β παντὶ τῷ Γ ὑπάρχειν καὶ τὸ Γ

παντὶ τῷ Α, συλλογισμὸς ἔσται τοῦ Β πρὸς τὸ Α. πάλιν

5 ἐὰν ληφθῇ τὸ μὲν Γ παντὶ τῷ Α, τὸ δὲ Α παντὶ τῷ Β,

παντὶ τῷ Β τὸ Γ ἀνάγκη ὑπάρχειν. ἐν ἀμφοτέροις δὴ τούτοις

τοῖς συλλογισμοῖς ἡ Γ Α πρότασις εἴληπται ἀναπόδεικτος·

αἱ γὰρ ἕτεραι δεδειγμέναι ἦσαν. ὥστ' ἂν ταύτην

ἀποδείξωμεν, ἅπασαι ἔσονται δεδειγμέναι δι' ἀλλήλων. ἐὰν

10 οὖν ληφθῇ τὸ Γ παντὶ τῷ Β καὶ τὸ Β παντὶ τῷ Α ὑπάρχειν,

ἀμφότεραί τε αἱ προτάσεις ἀποδεδειγμέναι λαμβάνονται,

καὶ τὸ Γ τῷ Α ἀνάγκη ὑπάρχειν. φανερὸν οὖν ὅτι

ἐν μόνοις τοῖς ἀντιστρέφουσι κύκλῳ καὶ δι' ἀλλήλων ἐνδέχεται

γίνεσθαι τὰς ἀποδείξεις, ἐν δὲ τοῖς ἄλλοις ὡς πρότερον

15 εἴπομεν. συμβαίνει δὲ καὶ ἐν τούτοις αὐτῷ τῷ δεικνυμένῳ

χρῆσθαι πρὸς τὴν ἀπόδειξιν· τὸ μὲν γὰρ Γ κατὰ τοῦ Β καὶ

τὸ Β κατὰ τοῦ Α δείκνυται ληφθέντος τοῦ Γ κατὰ τοῦ Α λέγεσθαι,

τὸ δὲ Γ κατὰ τοῦ Α διὰ τούτων δείκνυται τῶν προτάσεων,

ὥστε τῷ συμπεράσματι χρώμεθα πρὸς τὴν ἀπόδειξιν.

Ἐπὶ δὲ τῶν στερητικῶν συλλογισμῶν ὧδε δείκνυται ἐξ

ἀλλήλων. ἔστω τὸ μὲν Β παντὶ τῷ Γ ὑπάρχειν, τὸ δὲ Α οὐδενὶ

τῷ Β· συμπέρασμα ὅτι τὸ Α οὐδενὶ τῷ Γ. εἰ δὴ πάλιν

δεῖ συμπεράνασθαι ὅτι τὸ Α οὐδενὶ τῷ Β, ὃ πάλαι ἔλαβεν,

25 ἔστω τὸ μὲν Α μηδενὶ τῷ Γ, τὸ δὲ Γ παντὶ τῷ Β· οὕτω

γὰρ ἀνάπαλιν ἡ πρότασις. εἰ δ' ὅτι τὸ Β τῷ Γ δεῖ συμπεράνασθαι,

οὐκέθ' ὁμοίως ἀντιστρεπτέον τὸ Α Β (ἡ γὰρ αὐτὴ

πρότασις, τὸ Β μηδενὶ τῷ Α καὶ τὸ Α μηδενὶ τῷ Β ὑπάρχειν),

ἀλλὰ ληπτέον, ᾧ τὸ Α μηδενὶ ὑπάρχει, τὸ Β παντὶ

30 ὑπάρχειν. ἔστω τὸ Α μηδενὶ τῷ Γ ὑπάρχειν, ὅπερ ἦν τὸ

συμπέρασμα· ᾧ δὲ τὸ Α μηδενί, τὸ Β εἰλήφθω παντὶ

ὑπάρχειν· ἀνάγκη οὖν τὸ Β παντὶ τῷ Γ ὑπάρχειν. ὥστε

τριῶν ὄντων ἕκαστον συμπέρασμα γέγονε, καὶ τὸ κύκλῳ

ἀποδεικνύναι τοῦτ' ἔστι, τὸ τὸ συμπέρασμα λαμβάνοντα καὶ

35 ἀνάπαλιν τὴν ἑτέραν πρότασιν τὴν λοιπὴν συλλογίζεσθαι.

Ἐπὶ δὲ τῶν ἐν μέρει συλλογισμῶν τὴν μὲν καθόλου πρότασιν

οὐκ ἔστιν ἀποδεῖξαι διὰ τῶν ἑτέρων, τὴν δὲ κατὰ μέρος

ἔστιν. ὅτι μὲν οὖν οὐκ ἔστιν ἀποδεῖξαι τὴν καθόλου, φανερόν·

τὸ μὲν γὰρ καθόλου δείκνυται διὰ τῶν καθόλου, τὸ δὲ

40 συμπέρασμα οὐκ ἔστι καθόλου, δεῖ δ' ἐκ τοῦ συμπεράσματος

δεῖξαι καὶ τῆς ἑτέρας προτάσεως. ἔτι ὅλως οὐδὲ γίνεται

1Suppose the proposition AC has been demonstrated through B as middle term, and again the proposition AB through the conclusion and the premiss BC converted, and similarly the proposition BC through the conclusion and the premiss AB converted. But it is necessary to prove both the premiss CB, and the premiss BA: for we have used these alone without demonstrating them. If then it is assumed that B belongs to all C, and C to all A, we shall have a syllogism relating B to A. 5Again if it is assumed that C belongs to all A, and A to all B, C must belong to all B. In both these syllogisms the premiss CA has been assumed without being demonstrated: the other premisses had ex hypothesi been proved. Consequently if we succeed in demonstrating this premiss, all the premisses will have been proved reciprocally. 10If then it is assumed that C belongs to all B, and B to all A, both the premisses assumed have been proved, and C must belong to A. It is clear then that only if the terms are convertible is circular and reciprocal demonstration possible (if the terms are not convertible, the matter stands as we said above). 15But it turns out in these also that we use for the demonstration the very thing that is being proved: for C is proved of B, and B of by assuming that C is said of and C is proved of A through these premisses, so that we use the conclusion for the 20demonstration.
In negative syllogisms reciprocal proof is as follows. Let B belong to all C, and A to none of the Bs: we conclude that A belongs to none of the Cs. If again it is necessary to prove that A belongs to none of the Bs (which was previously assumed) 25A must belong to no C, and C to all B: thus the previous premiss is reversed. If it is necessary to prove that B belongs to C, the proposition AB must no longer be converted as before: for the premiss 'B belongs to no A' is identical with the premiss 'A belongs to no B'. But we must assume that B belongs to all of that to none of which longs. 30Let A belong to none of the Cs (which was the previous conclusion) and assume that B belongs to all of that to none of which A belongs. It is necessary then that B should belong to all C. Consequently each of the three propositions has been made a conclusion, and this is circular demonstration, to assume the conclusion and the converse of one of the premisses, 35and deduce the remaining premiss.
In particular syllogisms it is not possible to demonstrate the universal premiss through the other propositions, but the particular premiss can be demonstrated. Clearly it is impossible to demonstrate the universal premiss: for what is universal is proved through propositions which are universal, 40but the conclusion is not universal, and the proof must start from the conclusion and the other premiss.

58b

1 συλλογισμὸς ἀντιστραφείσης τῆς προτάσεως· ἐν μέρει γὰρ

ἀμφότεραι γίνονται αἱ προτάσεις. τὴν δ' ἐπὶ μέρους ἔστιν. δεδείχθω

γὰρ τὸ Α κατὰ τινὸς τοῦ Γ διὰ τοῦ Β. ἐὰν οὖν ληφθῇ

τὸ Β παντὶ τῷ Α καὶ τὸ συμπέρασμα μένῃ, τὸ Β τινὶ

5 τῷ Γ ὑπάρξει· γίνεται γὰρ τὸ πρῶτον σχῆμα, καὶ τὸ Α

μέσον. εἰ δὲ στερητικὸς ὁ συλλογισμός, τὴν μὲν καθόλου πρότασιν

οὐκ ἔστι δεῖξαι, δι' ὃ καὶ πρότερον ἐλέχθη· τὴν δ' ἐν μέρει

ἔστιν, ἐὰν ὁμοίως ἀντιστραφῇ τὸ Α Β ὥσπερ κἀπὶ τῶν καθόλου,

[οὐκ ἔστι, διὰ προσλήψεως δ' ἔστιν,] οἷον ᾧ τὸ Α τινὶ

10 μὴ ὑπάρχει, τὸ Β τινὶ ὑπάρχειν· ἄλλως γὰρ οὐ γίνεται

συλλογισμὸς διὰ τὸ ἀποφατικὴν εἶναι τὴν ἐν μέρει πρότασιν.

1Further a syllogism cannot be made at all if the other premiss is converted: for the result is that both premisses are particular. But the particular premiss may be proved. Suppose that A has been proved of some C through B. If then it is assumed that B belongs to all A and the conclusion is retained, 5B will belong to some C: for we obtain the first figure and A is middle. But if the syllogism is negative, it is not possible to prove the universal premiss, for the reason given above. But it is possible to prove the particular premiss, if the proposition AB is converted as in the universal syllogism, i.e '10B belongs to some of that to some of which A does not belong': otherwise no syllogism results because the particular premiss is negative.

Book 2,Chapter 6 (58b13–38)

Ἐν δὲ τῷ δευτέρῳ σχήματι τὸ μὲν καταφατικὸν οὐκ

ἔστι δεῖξαι διὰ τούτου τοῦ τρόπου, τὸ δὲ στερητικὸν ἔστιν. τὸ μὲν

15 οὖν κατηγορικὸν οὐ δείκνυται διὰ τὸ μὴ ἀμφοτέρας εἶναι

τὰς προτάσεις καταφατικάς· τὸ γὰρ συμπέρασμα στερητικόν

ἐστι, τὸ δὲ κατηγορικὸν ἐξ ἀμφοτέρων ἐδείκνυτο καταφατικῶν.

τὸ δὲ στερητικὸν ὧδε δείκνυται. ὑπαρχέτω τὸ Α

παντὶ τῷ Β, τῷ δὲ Γ μηδενί· συμπέρασμα τὸ Β οὐδενὶ

20 τῷ Γ. ἐὰν οὖν ληφθῇ τὸ Β παντὶ τῷ Α ὑπάρχον, [τῷ δὲ Γ

μηδενί,] ἀνάγκη τὸ Α μηδενὶ τῷ Γ ὑπάρχειν· γίνεται γὰρ

τὸ δεύτερον σχῆμα· μέσον τὸ Β. εἰ δὲ τὸ Α Β στερητικὸν

ἐλήφθη, θάτερον δὲ κατηγορικόν, τὸ πρῶτον ἔσται σχῆμα.

τὸ μὲν γὰρ Γ παντὶ τῷ Α, τὸ δὲ Β οὐδενὶ τῷ Γ, ὥστ' οὐδενὶ

25 τῷ Α τὸ Β· οὐδ' ἄρα τὸ Α τῷ Β. διὰ μὲν οὖν τοῦ

συμπεράσματος καὶ τῆς μιᾶς προτάσεως οὐ γίνεται συλλογισμός,

προσληφθείσης δ' ἑτέρας ἔσται. εἰ δὲ μὴ καθόλου

ὁ συλλογισμός, ἡ μὲν ἐν ὅλῳ πρότασις οὐ δείκνυται

διὰ τὴν αὐτὴν αἰτίαν ἥνπερ εἴπομεν καὶ πρότερον, ἡ δ' ἐν μέρει

30 δείκνυται, ὅταν ᾖ τὸ καθόλου κατηγορικόν· ὑπαρχέτω

γὰρ τὸ Α παντὶ τῷ Β, τῷ δὲ Γ μὴ παντί· συμπέρασμα Β Γ.

ἐὰν οὖν ληφθῇ τὸ Β παντὶ τῷ Α, τῷ δὲ Γ οὐ παντί, τὸ Α

τινὶ τῷ Γ οὐχ ὑπάρξει· μέσον Β. εἰ δ' ἐστὶν ἡ καθόλου στερητική,

οὐ δειχθήσεται ἡ Α Γ πρότασις ἀντιστραφέντος τοῦ Α Β·

35 συμβαίνει γὰρ ἢ ἀμφοτέρας ἢ τὴν ἑτέραν πρότασιν γίνεσθαι

ἀποφατικήν, ὥστ' οὐκ ἔσται συλλογισμός. ἀλλ' ὁμοίως

δειχθήσεται ὡς καὶ ἐπὶ τῶν καθόλου, ἐὰν ληφθῇ, ᾧ τὸ Β

τινὶ μὴ ὑπάρχει, τὸ Α τινὶ ὑπάρχειν.

13In the second figure it is not possible to prove an affirmative proposition in this way, but a negative proposition may be proved. An affirmative proposition 15is not proved because both premisses of the new syllogism are not affirmative (for the conclusion is negative) but an affirmative proposition is (as we saw) proved from premisses which are both affirmative. The negative is proved as follows. Let A belong to all B, and to no C: we conclude that B belongs to no C. 20If then it is assumed that B belongs to all A, it is necessary that A should belong to no C: for we get the second figure, with B as middle. But if the premiss AB was negative, and the other affirmative, we shall have the first figure. For C belongs to all A and B to no C, consequently B belongs to no A: 25neither then does A belong to B. Through the conclusion, therefore, and one premiss, we get no syllogism, but if another premiss is assumed in addition, a syllogism will be possible. But if the syllogism not universal, the universal premiss cannot be proved, for the same reason as we gave above, but the particular premiss 30can be proved whenever the universal statement is affirmative. Let A belong to all B, and not to all C: the conclusion is BC. If then it is assumed that B belongs to all A, but not to all C, A will not belong to some C, B being middle. But if the universal premiss is negative, the premiss AC will not be demonstrated by the conversion of AB: 35for it turns out that either both or one of the premisses is negative; consequently a syllogism will not be possible. But the proof will proceed as in the universal syllogisms, if it is assumed that A belongs to some of that to some of which B does not belong.

Book 2,Chapter 7 (58b39–59a41)

Ἐπὶ δὲ τοῦ τρίτου σχήματος ὅταν μὲν ἀμφότεραι αἱ

40 προτάσεις καθόλου ληφθῶσιν, οὐκ ἐνδέχεται δεῖξαι δι' ἀλλήλων·

τὸ μὲν γὰρ καθόλου δείκνυται διὰ τῶν καθόλου, τὸ

39In the third figure, when both 40premisses are taken universally, it is not possible to prove them reciprocally: for that which is universal is proved through statements which are universal, but the conclusion in this figure is always particular, so that it is clear that it is not possible at all to prove through this figure the universal premiss.

59a

1 δ' ἐν τούτῳ συμπέρασμα ἀεὶ κατὰ μέρος, ὥστε φανερὸν ὅτι

ὅλως οὐκ ἐνδέχεται δεῖξαι διὰ τούτου τοῦ σχήματος τὴν

καθόλου πρότασιν. Ἐὰν δ' ἡ μὲν ᾖ καθόλου ἡ δ' ἐν μέρει,

ποτὲ μὲν ἔσται ποτὲ δ' οὐκ ἔσται. ὅταν μὲν οὖν ἀμφότεραι

5 κατηγορικαὶ ληφθῶσι καὶ τὸ καθόλου γένηται πρὸς τῷ ἐλάττονι

ἄκρῳ, ἔσται, ὅταν δὲ πρὸς θατέρῳ, οὐκ ἔσται. ὑπαρχέτω

γὰρ τὸ Α παντὶ τῷ Γ, τὸ δὲ Β τινί· συμπέρασμα

τὸ Α Β. ἐὰν οὖν ληφθῇ τὸ Γ παντὶ τῷ Α ὑπάρχειν, τὸ μὲν

Γ δέδεικται τινὶ τῷ Β ὑπάρχον, τὸ δὲ Β τινὶ τῷ Γ οὐ δέδεικται.

10 καίτοι ἀνάγκη, εἰ τὸ Γ τινὶ τῷ Β, καὶ τὸ Β τινὶ

τῷ Γ ὑπάρχειν. ἀλλ' οὐ ταὐτόν ἐστι τόδε τῷδε καὶ τόδε

τῷδε ὑπάρχειν· ἀλλὰ προσληπτέον, εἰ τόδε τινὶ τῷδε, καὶ

θάτερον τινὶ τῷδε. τούτου δὲ ληφθέντος οὐκέτι γίνεται ἐκ τοῦ

συμπεράσματος καὶ τῆς ἑτέρας προτάσεως ὁ συλλογισμός.

15 εἰ δὲ τὸ Β παντὶ τῷ Γ, τὸ δὲ Α τινὶ τῷ Γ, ἔσται δεῖξαι

τὸ Α Γ, ὅταν ληφθῇ τὸ μὲν Γ παντὶ τῷ Β ὑπάρχειν,

τὸ δὲ Α τινί. εἰ γὰρ τὸ Γ παντὶ τῷ Β, τὸ δὲ Α τινὶ τῷ Β,

ἀνάγκη τὸ Α τινὶ τῷ Γ ὑπάρχειν· μέσον τὸ Β. καὶ ὅταν ᾖ

ἡ μὲν κατηγορικὴ ἡ δὲ στερητική, καθόλου δ' ἡ κατηγορική,

20 δειχθήσεται ἡ ἑτέρα. ὑπαρχέτω γὰρ τὸ Β παντὶ τῷ Γ, τὸ

δὲ Α τινὶ μὴ ὑπαρχέτω· συμπέρασμα ὅτι τὸ Α τινὶ τῷ Β

οὐχ ὑπάρχει. ἐὰν οὖν προσληφθῇ τὸ Γ παντὶ τῷ Β ὑπάρχειν,

ἀνάγκη τὸ Α τινὶ τῷ Γ μὴ ὑπάρχειν· μέσον τὸ Β.

ὅταν δ' ἡ στερητικὴ καθόλου γένηται, οὐ δείκνυται ἡ ἑτέρα,

25 εἰ μὴ ὥσπερ ἐπὶ τῶν πρότερον, ἐὰν ληφθῇ, ᾧ τοῦτο τινὶ

μὴ ὑπάρχει, θάτερον τινὶ ὑπάρχειν, οἷον εἰ τὸ μὲν Α μηδενὶ

τῷ Γ, τὸ δὲ Β τινί· συμπέρασμα ὅτι τὸ Α τινὶ τῷ Β

οὐχ ὑπάρχει. ἐὰν οὖν ληφθῇ, ᾧ τὸ Α τινὶ μὴ ὑπάρχει,

τὸ Γ τινὶ ὑπάρχειν, ἀνάγκη τὸ Γ τινὶ τῷ Β ὑπάρχειν. ἄλλως

30 δ' οὐκ ἔστιν ἀντιστρέφοντα τὴν καθόλου πρότασιν δεῖξαι

τὴν ἑτέραν· οὐδαμῶς γὰρ ἔσται συλλογισμός.

[Φανερὸν οὖν ὅτι ἐν μὲν τῷ πρώτῳ σχήματι ἡ δι' ἀλλήλων

δεῖξις διά τε τοῦ τρίτου καὶ διὰ τοῦ πρώτου γίνεται σχήματος.

κατηγορικοῦ μὲν γὰρ ὄντος τοῦ συμπεράσματος διὰ

35 τοῦ πρώτου, στερητικοῦ δὲ διὰ τοῦ ἐσχάτου· λαμβάνεται

γάρ, ᾧ τοῦτο μηδενί, θάτερον παντὶ ὑπάρχειν. ἐν δὲ τῷ μέσῳ

καθόλου μὲν ὄντος τοῦ συλλογισμοῦ δι' αὐτοῦ τε καὶ διὰ τοῦ

πρώτου σχήματος, ὅταν δ' ἐν μέρει, δι' αὐτοῦ τε καὶ τοῦ

ἐσχάτου. ἐν δὲ τῷ τρίτῳ δι' αὐτοῦ πάντες. φανερὸν δὲ καὶ

40 ὅτι ἐν τῷ τρίτῳ καὶ τῷ μέσῳ οἱ μὴ δι' αὐτῶν γινόμενοι

συλλογισμοὶ ἢ οὐκ εἰσὶ κατὰ τὴν κύκλῳ δεῖξιν ἢ ἀτελεῖς.]

1But if one premiss is universal, the other particular, proof of the latter will sometimes be possible, sometimes not. When both the 5premisses assumed are affirmative, and the universal concerns the minor extreme, proof will be possible, but when it concerns the other extreme, impossible. Let A belong to all C and B to some C: the conclusion is the statement AB. If then it is assumed that C belongs to all A, it has been proved that C belongs to some B, but that B belongs to some C has not been proved. 10And yet it is necessary, if C belongs to some B, that B should belong to some C. But it is not the same that this should belong to that, and that to this: but we must assume besides that if this belongs to some of that, that belongs to some of this. But if this is assumed the syllogism no longer results from the conclusion and the other premiss. 15But if B belongs to all C, and A to some C, it will be possible to prove the proposition AC, when it is assumed that C belongs to all B, and A to some B. For if C belongs to all B and A to some B, it is necessary that A should belong to some C, B being middle. And whenever one premiss is affirmative the other negative, and the affirmative is universal, 20the other premiss can be proved. Let B belong to all C, and A not to some C: the conclusion is that A does not belong to some B. If then it is assumed further that C belongs to all B, it is necessary that A should not belong to some C, B being middle. But when the negative premiss is universal, the other premiss is not 25except as before, viz. if it is assumed that that belongs to some of that, to some of which this does not belong, e.g. if A belongs to no C, and B to some C: the conclusion is that A does not belong to some B. If then it is assumed that C belongs to some of that to some of which does not belong, it is necessary that C should belong to some of the Bs. 30In no other way is it possible by converting the universal premiss to prove the other: for in no other way can a syllogism be formed.
It is clear then that in the first figure reciprocal proof is made both through the third and through the first figure-if the conclusion is affirmative through the first; 35if the conclusion is negative through the last. For it is assumed that that belongs to all of that to none of which this belongs. In the middle figure, when the syllogism is universal, proof is possible through the second figure and through the first, but when particular through the second and the last. In the third figure all proofs are made through itself. It is clear also that 40in the third figure and in the middle figure those syllogisms which are not made through those figures themselves either are not of the nature of circular proof or are imperfect.

Book 2,Chapter 8 (59b1–60a14)

59b

1 Τὸ δ' ἀντιστρέφειν ἐστὶ τὸ μετατιθέντα τὸ συμπέρασμα

ποιεῖν τὸν συλλογισμὸν ὅτι ἢ τὸ ἄκρον τῷ μέσῳ οὐχ ὑπάρξει

ἢ τοῦτο τῷ τελευταίῳ. ἀνάγκη γὰρ τοῦ συμπεράσματος

ἀντιστραφέντος καὶ τῆς ἑτέρας μενούσης προτάσεως ἀναιρεῖσθαι

5 τὴν λοιπήν· εἰ γὰρ ἔσται, καὶ τὸ συμπέρασμα ἔσται.

διαφέρει δὲ τὸ ἀντικειμένως ἢ ἐναντίως ἀντιστρέφειν τὸ συμπέρασμα·

οὐ γὰρ ὁ αὐτὸς γίνεται συλλογισμὸς ἑκατέρως

ἀντιστραφέντος· δῆλον δὲ τοῦτ' ἔσται διὰ τῶν ἑπομένων. λέγω

δ' ἀντικεῖσθαι μὲν τὸ παντὶ τῷ οὐ παντὶ καὶ τὸ τινὶ τῷ οὐδενί,

10 ἐναντίως δὲ τὸ παντὶ τῷ οὐδενὶ καὶ τὸ τινὶ τῷ οὐ τινὶ

ὑπάρχειν. ἔστω γὰρ δεδειγμένον τὸ Α κατὰ τοῦ Γ διὰ μέσου

τοῦ Β. εἰ δὴ τὸ Α ληφθείη μηδενὶ τῷ Γ ὑπάρχειν, τῷ

δὲ Β παντί, οὐδενὶ τῷ Γ ὑπάρξει τὸ Β. καὶ εἰ τὸ μὲν Α

μηδενὶ τῷ Γ, τὸ δὲ Β παντὶ τῷ Γ, τὸ Α οὐ παντὶ τῷ Β

15 καὶ οὐχ ἁπλῶς οὐδενί· οὐ γὰρ ἐδείκνυτο τὸ καθόλου διὰ τοῦ

ἐσχάτου σχήματος. ὅλως δὲ τὴν πρὸς τῷ μείζονι ἄκρῳ

πρότασιν οὐκ ἔστιν ἀνασκευάσαι καθόλου διὰ τῆς ἀντιστροφῆς·

ἀεὶ γὰρ ἀναιρεῖται διὰ τοῦ τρίτου σχήματος· ἀνάγκη

γὰρ πρὸς τὸ ἔσχατον ἄκρον ἀμφοτέρας λαβεῖν τὰς προτάσεις.

20 καὶ εἰ στερητικὸς ὁ συλλογισμός, ὡσαύτως. δεδείχθω

γὰρ τὸ Α μηδενὶ τῷ Γ ὑπάρχον διὰ τοῦ Β. οὐκοῦν ἂν ληφθῇ

τὸ Α τῷ Γ παντὶ ὑπάρχειν, τῷ δὲ Β μηδενί, οὐδενὶ

τῷ Γ τὸ Β ὑπάρξει. καὶ εἰ τὸ Α καὶ τὸ Β παντὶ τῷ Γ,

τὸ Α τινὶ τῷ Β· ἀλλ' οὐδενὶ ὑπῆρχεν.

25 Ἐὰν δ' ἀντικειμένως ἀντιστραφῇ τὸ συμπέρασμα, καὶ

οἱ συλλογισμοὶ ἀντικείμενοι καὶ οὐ καθόλου ἔσονται. γίνεται

γὰρ ἡ ἑτέρα πρότασις ἐν μέρει, ὥστε καὶ τὸ συμπέρασμα

ἔσται κατὰ μέρος. ἔστω γὰρ κατηγορικὸς ὁ συλλογισμός,

καὶ ἀντιστρεφέσθω οὕτως. οὐκοῦν εἰ τὸ Α οὐ παντὶ

30 τῷ Γ, τῷ δὲ Β παντί, τὸ Β οὐ παντὶ τῷ Γ· καὶ εἰ τὸ μὲν

Α μὴ παντὶ τῷ Γ, τὸ δὲ Β παντί, τὸ Α οὐ παντὶ τῷ Β.

ὁμοίως δὲ καὶ εἰ στερητικὸς ὁ συλλογισμός. εἰ γὰρ τὸ Α

τινὶ τῷ Γ ὑπάρχει, τῷ δὲ Β μηδενί, τὸ Β τινὶ τῷ Γ οὐχ

ὑπάρξει, οὐχ ἁπλῶς οὐδενί· καὶ εἰ τὸ μὲν Α τῷ Γ τινί,

35 τὸ δὲ Β παντί, ὥσπερ ἐν ἀρχῇ ἐλήφθη, τὸ Α τινὶ τῷ Β

ὑπάρξει.

Ἐπὶ δὲ τῶν ἐν μέρει συλλογισμῶν ὅταν μὲν ἀντικειμένως

ἀντιστρέφηται τὸ συμπέρασμα, ἀναιροῦνται ἀμφότεραι

αἱ προτάσεις, ὅταν δ' ἐναντίως, οὐδετέρα. οὐ γὰρ ἔτι

40 συμβαίνει, καθάπερ ἐν τοῖς καθόλου, ἀναιρεῖν ἐλλείποντος

τοῦ συμπεράσματος κατὰ τὴν ἀντιστροφήν, ἀλλ' οὐδ' ὅλως

1To convert a syllogism means to alter the conclusion and make another syllogism to prove that either the extreme cannot belong to the middle or the middle to the last term. For it is necessary, if the conclusion has been changed into its opposite and one of the premisses stands, that the other premiss should be destroyed. 5For if it should stand, the conclusion also must stand. It makes a difference whether the conclusion is converted into its contradictory or into its contrary. For the same syllogism does not result whichever form the conversion takes. This will be made clear by the sequel. By contradictory opposition I mean the opposition of 'to all' to 'not to all', and of 'to some' to 'to none'; 10by contrary opposition I mean the opposition of 'to all' to 'to none', and of 'to some' to 'not to some'. Suppose that A been proved of C, through B as middle term. If then it should be assumed that A belongs to no C, but to all B, B will belong to no C. And if A belongs to no C, and B to all C, A will belong, not to no B at all, 15but not to all B. For (as we saw) the universal is not proved through the last figure. In a word it is not possible to refute universally by conversion the premiss which concerns the major extreme: for the refutation always proceeds through the third since it is necessary to take both premisses in reference to the minor extreme. 20Similarly if the syllogism is negative. Suppose it has been proved that A belongs to no C through B. Then if it is assumed that A belongs to all C, and to no B, B will belong to none of the Cs. And if A and B belong to all C, A will belong to some B: but in the original premiss it belonged to no B.
25If the conclusion is converted into its contradictory, the syllogisms will be contradictory and not universal. For one premiss is particular, so that the conclusion also will be particular. Let the syllogism be affirmative, and let it be converted as stated. Then if A belongs not 30to all C, but to all B, B will belong not to all C. And if A belongs not to all C, but B belongs to all C, A will belong not to all B. Similarly if the syllogism is negative. For if A belongs to some C, and to no B, B will belong, not to no C at all, but-not to some C. And if A belongs to some C, 35and B to all C, as was originally assumed, A will belong to some B.
In particular syllogisms when the conclusion is converted into its contradictory, both premisses may be refuted, but when it is converted into its contrary, neither. For the result is no longer, 40as in the universal syllogisms, refutation in which the conclusion reached by O, conversion lacks universality, but no refutation at all. Suppose that A has been proved of some C.

60a

1 ἀναιρεῖν. δεδείχθω γὰρ τὸ Α κατὰ τινὸς τοῦ Γ. οὐκοῦν ἂν

ληφθῇ τὸ Α μηδενὶ τῷ Γ ὑπάρχειν, τὸ δὲ Β τινί, τὸ Α

τῷ Β τινὶ οὐχ ὑπάρξει· καὶ εἰ τὸ Α μηδενὶ τῷ Γ, τῷ δὲ

Β παντί, οὐδενὶ τῷ Γ τὸ Β. ὥστ' ἀναιροῦνται ἀμφότεραι.

5 ἐὰν δ' ἐναντίως ἀντιστραφῇ, οὐδετέρα. εἰ γὰρ τὸ Α τινὶ τῷ

Γ μὴ ὑπάρχει, τῷ δὲ Β παντί, τὸ Β τινὶ τῷ Γ οὐχ

ὑπάρξει, ἀλλ' οὔπω ἀναιρεῖται τὸ ἐξ ἀρχῆς· ἐνδέχεται

γὰρ τινὶ ὑπάρχειν καὶ τινὶ μὴ ὑπάρχειν. τῆς δὲ καθόλου,

τῆς Α Β, ὅλως οὐδὲ γίνεται συλλογισμός· εἰ γὰρ τὸ μὲν

10 Α τινὶ τῷ Γ μὴ ὑπάρχει, τὸ δὲ Β τινὶ ὑπάρχει, οὐδετέρα

καθόλου τῶν προτάσεων. ὁμοίως δὲ καὶ εἰ στερητικὸς ὁ συλλογισμός·

εἰ μὲν γὰρ ληφθείη τὸ Α παντὶ τῷ Γ ὑπάρχειν,

ἀναιροῦνται ἀμφότεραι, εἰ δὲ τινί, οὐδετέρα. ἀπόδειξις

δ' ἡ αὐτή.

1If then it is assumed that A belongs to no C, and B to some C, A will not belong to some B: and if A belongs to no C, but to all B, B will belong to no C. Thus both premisses are refuted. 5But neither can be refuted if the conclusion is converted into its contrary. For if A does not belong to some C, but to all B, then B will not belong to some C. But the original premiss is not yet refuted: for it is possible that B should belong to some C, and should not belong to some C. The universal premiss AB cannot be affected by a syllogism at all: 10for if A does not belong to some of the Cs, but B belongs to some of the Cs, neither of the premisses is universal. Similarly if the syllogism is negative: for if it should be assumed that A belongs to all C, both premisses are refuted: but if the assumption is that A belongs to some C, neither premiss is refuted. The proof is the same as before.

Book 2,Chapter 9 (60a15–60b5)

15 Ἐν δὲ τῷ δευτέρῳ σχήματι τὴν μὲν πρὸς τῷ μείζονι

ἄκρῳ πρότασιν οὐκ ἔστιν ἀνελεῖν ἐναντίως, ὁποτερωσοῦν τῆς

ἀντιστροφῆς γινομένης· ἀεὶ γὰρ ἔσται τὸ συμπέρασμα ἐν τῷ

τρίτῳ σχήματι, καθόλου δ' οὐκ ἦν ἐν τούτῳ συλλογισμός.

τὴν δ' ἑτέραν ὁμοίως ἀναιρήσομεν τῇ ἀντιστροφῇ. λέγω δὲ

20 τὸ ὁμοίως, εἰ μὲν ἐναντίως ἀντιστρέφεται, ἐναντίως, εἰ δ'

ἀντικειμένως, ἀντικειμένως. ὑπαρχέτω γὰρ τὸ Α παντὶ τῷ

Β, τῷ δὲ Γ μηδενί· συμπέρασμα Β Γ. ἐὰν οὖν ληφθῇ τὸ

Β παντὶ τῷ Γ ὑπάρχειν καὶ τὸ Α Β μένῃ, τὸ Α παντὶ τῷ

Γ ὑπάρξει· γίνεται γὰρ τὸ πρῶτον σχῆμα. εἰ δὲ τὸ Β

25 παντὶ τῷ Γ, τὸ δὲ Α μηδενὶ τῷ Γ, τὸ Α οὐ παντὶ τῷ Β·

σχῆμα τὸ ἔσχατον. ἐὰν δ' ἀντικειμένως ἀντιστραφῇ τὸ Β Γ,

ἡ μὲν Α Β ὁμοίως δειχθήσεται, ἡ δὲ Α Γ ἀντικειμένως. εἰ

γὰρ τὸ Β τινὶ τῷ Γ, τὸ δὲ Α μηδενὶ τῷ Γ, τὸ Α τινὶ τῷ

Β οὐχ ὑπάρξει. πάλιν εἰ τὸ Β τινὶ τῷ Γ, τὸ δὲ Α παντὶ

30 τῷ Β, τὸ Α τινὶ τῷ Γ, ὥστ' ἀντικείμενος γίνεται ὁ συλλογισμός.

ὁμοίως δὲ δειχθήσεται καὶ εἰ ἀνάπαλιν ἔχοιεν αἱ

προτάσεις. εἰ δ' ἐστὶν ἐπὶ μέρους ὁ συλλογισμός, ἐναντίως

μὲν ἀντιστρεφομένου τοῦ συμπεράσματος οὐδετέρα τῶν προτάσεων

ἀναιρεῖται, καθάπερ οὐδ' ἐν τῷ πρώτῳ σχήματι,

35 ἀντικειμένως δ' ἀμφότεραι. κείσθω γὰρ τὸ Α τῷ μὲν Β

μηδενὶ ὑπάρχειν, τῷ δὲ Γ τινί· συμπέρασμα Β Γ. ἐὰν οὖν

τεθῇ τὸ Β τινὶ τῷ Γ ὑπάρχειν καὶ τὸ Α Β μένῃ, συμπέρασμα

ἔσται ὅτι τὸ Α τινὶ τῷ Γ οὐχ ὑπάρχει, ἀλλ' οὐκ

ἀνῄρηται τὸ ἐξ ἀρχῆς· ἐνδέχεται γὰρ τινὶ ὑπάρχειν καὶ μὴ

40 ὑπάρχειν. πάλιν εἰ τὸ Β τινὶ τῷ Γ καὶ τὸ Α τινὶ τῷ Γ, οὐκ

ἔσται συλλογισμός· οὐδέτερον γὰρ καθόλου τῶν εἰλημμένων.

15In the second figure it is not possible to refute the premiss which concerns the major extreme by establishing something contrary to it, whichever form the conversion of the conclusion may take. For the conclusion of the refutation will always be in the third figure, and in this figure (as we saw) there is no universal syllogism. The other premiss can be refuted in a manner similar to the conversion: I mean, 20if the conclusion of the first syllogism is converted into its contrary, the conclusion of the refutation will be the contrary of the minor premiss of the first, if into its contradictory, the contradictory. Let A belong to all B and to no C: conclusion BC. If then it is assumed that B belongs to all C, and the proposition AB stands, A will belong to all C, since the first figure is produced. If B belongs to all C, 25and A to no C, then A belongs not to all B: the figure is the last. But if the conclusion BC is converted into its contradictory, the premiss AB will be refuted as before, the premiss, AC by its contradictory. For if B belongs to some C, and A to no C, then A will not belong to some B. Again if B belongs to some C, and A to all B, 30A will belong to some C, so that the syllogism results in the contradictory of the minor premiss. A similar proof can be given if the premisses are transposed in respect of their quality.
If the syllogism is particular, when the conclusion is converted into its contrary neither premiss can be refuted, as also happened in the first figure,' if the conclusion is converted into its contradictory, 35both premisses can be refuted. Suppose that A belongs to no B, and to some C: the conclusion is BC. If then it is assumed that B belongs to some C, and the statement AB stands, the conclusion will be that A does not belong to some C. But the original statement has not been refuted: for it is possible that A should belong to some C and also not to some C. 40Again if B belongs to some C and A to some C, no syllogism will be possible: for neither of the premisses taken is universal.

60b

1 ὥστ' οὐκ ἀναιρεῖται τὸ Α Β. ἐὰν δ' ἀντικειμένως ἀντιστρέφηται,

ἀναιροῦνται ἀμφότεραι. εἰ γὰρ τὸ Β παντὶ τῷ Γ, τὸ

δὲ Α μηδενὶ τῷ Β, οὐδενὶ τῷ Γ τὸ Α· ἦν δὲ τινί. πάλιν

εἰ τὸ Β παντὶ τῷ Γ, τὸ δὲ Α τινὶ τῷ Γ, τινὶ τῷ Β τὸ Α.

5 ἡ αὐτὴ δ' ἀπόδειξις καὶ εἰ τὸ καθόλου κατηγορικόν.

1Consequently the proposition AB is not refuted. But if the conclusion is converted into its contradictory, both premisses can be refuted. For if B belongs to all C, and A to no B, A will belong to no C: but it was assumed to belong to some C. Again if B belongs to all C and A to some C, A will belong to some B. 5The same proof can be given if the universal statement is affirmative.

Book 2,Chapter 10 (60b6–61a16)

Ἐπὶ δὲ τοῦ τρίτου σχήματος ὅταν μὲν ἐναντίως ἀντιστρέφηται

τὸ συμπέρασμα, οὐδετέρα τῶν προτάσεων ἀναιρεῖται

κατ' οὐδένα τῶν συλλογισμῶν, ὅταν δ' ἀντικειμένως,

ἀμφότεραι καὶ ἐν ἅπασιν. δεδείχθω γὰρ τὸ Α τινὶ τῷ Β

10 ὑπάρχον, μέσον δ' εἰλήφθω τὸ Γ, ἔστωσαν δὲ καθόλου αἱ

προτάσεις. οὐκοῦν ἐὰν ληφθῇ τὸ Α τινὶ τῷ Β μὴ ὑπάρχειν,

τὸ δὲ Β παντὶ τῷ Γ, οὐ γίνεται συλλογισμὸς τοῦ Α καὶ

τοῦ Γ. οὐδ' εἰ τὸ Α τῷ μὲν Β τινὶ μὴ ὑπάρχει, τῷ δὲ Γ

παντί, οὐκ ἔσται τοῦ Β καὶ τοῦ Γ συλλογισμός. ὁμοίως δὲ

15 δειχθήσεται καὶ εἰ μὴ καθόλου αἱ προτάσεις. ἢ γὰρ ἀμφοτέρας

ἀνάγκη κατὰ μέρος εἶναι διὰ τῆς ἀντιστροφῆς, ἢ τὸ

καθόλου πρὸς τῷ ἐλάττονι ἄκρῳ γίνεσθαι· οὕτω δ' οὐκ ἦν

συλλογισμὸς οὔτ' ἐν τῷ πρώτῳ σχήματι οὔτ' ἐν τῷ μέσῳ.

ἐὰν δ' ἀντικειμένως ἀντιστρέφηται, αἱ προτάσεις ἀναιροῦνται

20 ἀμφότεραι. εἰ γὰρ τὸ Α μηδενὶ τῷ Β, τὸ δὲ Β παντὶ

τῷ Γ, τὸ Α οὐδενὶ τῷ Γ· πάλιν εἰ τὸ Α τῷ μὲν Β μηδενί,

τῷ δὲ Γ παντί, τὸ Β οὐδενὶ τῷ Γ. καὶ εἰ ἡ ἑτέρα

μὴ καθόλου, ὡσαύτως. εἰ γὰρ τὸ Α μηδενὶ τῷ Β, τὸ δὲ Β

τινὶ τῷ Γ, τὸ Α τινὶ τῷ Γ οὐχ ὑπάρξει· εἰ δὲ τὸ Α τῷ

25 μὲν Β μηδενί, τῷ δὲ Γ παντί, οὐδενὶ τῷ Γ τὸ Β. Ὁμοίως

δὲ καὶ εἰ στερητικὸς ὁ συλλογισμός. δεδείχθω γὰρ τὸ Α

τινὶ τῷ Β μὴ ὑπάρχον, ἔστω δὲ κατηγορικὸν μὲν τὸ Β Γ,

ἀποφατικὸν δὲ τὸ Α Γ· οὕτω γὰρ ἐγίνετο ὁ συλλογισμός.

ὅταν μὲν οὖν τὸ ἐναντίον ληφθῇ τῷ συμπεράσματι, οὐκ ἔσται

30 συλλογισμός. εἰ γὰρ τὸ Α τινὶ τῷ Β, τὸ δὲ Β παντὶ τῷ

Γ, οὐκ ἦν συλλογισμὸς τοῦ Α καὶ τοῦ Γ. οὐδ' εἰ τὸ Α τινὶ τῷ

Β, τῷ δὲ Γ μηδενί, οὐκ ἦν τοῦ Β καὶ τοῦ Γ συλλογισμός.

ὥστε οὐκ ἀναιροῦνται αἱ προτάσεις. ὅταν δὲ τὸ ἀντικείμενον,

ἀναιροῦνται. εἰ γὰρ τὸ Α παντὶ τῷ Β καὶ τὸ Β τῷ Γ, τὸ

35 Α παντὶ τῷ Γ· ἀλλ' οὐδενὶ ὑπῆρχεν. πάλιν εἰ τὸ Α παντὶ

τῷ Β, τῷ δὲ Γ μηδενί, τὸ Β οὐδενὶ τῷ Γ· ἀλλὰ παντὶ

ὑπῆρχεν. ὁμοίως δὲ δείκνυται καὶ εἰ μὴ καθόλου εἰσὶν αἱ

προτάσεις. γίνεται γὰρ τὸ Α Γ καθόλου τε καὶ στερητικόν,

θάτερον δ' ἐπὶ μέρους καὶ κατηγορικόν. εἰ μὲν οὖν τὸ Α παντὶ

40 τῷ Β, τὸ δὲ Β τινὶ τῷ Γ, τὸ Α τινὶ τῷ Γ συμβαίνει·

ἀλλ' οὐδενὶ ὑπῆρχεν. πάλιν εἰ τὸ Α παντὶ τῷ Β, τῷ δὲ Γ

6In the third figure when the conclusion is converted into its contrary, neither of the premisses can be refuted in any of the syllogisms, but when the conclusion is converted into its contradictory, both premisses may be refuted and in all the moods. Suppose it has been proved that A belongs to some B, 10C being taken as middle, and the premisses being universal. If then it is assumed that A does not belong to some B, but B belongs to all C, no syllogism is formed about A and C. Nor if A does not belong to some B, but belongs to all C, will a syllogism be possible about B and C. A similar proof can be given 15if the premisses are not universal. For either both premisses arrived at by the conversion must be particular, or the universal premiss must refer to the minor extreme. But we found that no syllogism is possible thus either in the first or in the middle figure. But if the conclusion is converted into its contradictory, both the premisses can be refuted. 20For if A belongs to no B, and B to all C, then A belongs to no C: again if A belongs to no B, and to all C, B belongs to no C. And similarly if one of the premisses is not universal. For if A belongs to no B, and B to some C, A will not belong to some C: if A belongs to no B, 25and to C, B will belong to no C.
Similarly if the original syllogism is negative. Suppose it has been proved that A does not belong to some B, BC being affirmative, AC being negative: for it was thus that, as we saw, a syllogism could be made. Whenever then the contrary of the conclusion is assumed a syllogism will not be possible. 30For if A belongs to some B, and B to all C, no syllogism is possible (as we saw) about A and C. Nor, if A belongs to some B, and to no C, was a syllogism possible concerning B and C. Therefore the premisses are not refuted. But when the contradictory of the conclusion is assumed, they are refuted. For if A belongs to all B, and B to C, 35A belongs to all C: but A was supposed originally to belong to no C. Again if A belongs to all B, and to no C, then B belongs to no C: but it was supposed to belong to all C. A similar proof is possible if the premisses are not universal. For AC becomes universal and negative, the other premiss particular and affirmative. If then A belongs to all B, 40and B to some C, it results that A belongs to some C: but it was supposed to belong to no C. Again if A belongs to all B, and to no C, then B belongs to no C: but it was assumed to belong to some C.

61a

1 μηδενί, τὸ Β οὐδενὶ τῷ Γ· ἔκειτο δὲ τινί. εἰ δὲ τὸ Α τινὶ

τῷ Β καὶ τὸ Β τινὶ τῷ Γ, οὐ γίνεται συλλογισμός· οὐδ'

εἰ τὸ Α τινὶ τῷ Β, τῷ δὲ Γ μηδενί, οὐδ' οὕτως. ὥστ' ἐκείνως

μὲν ἀναιροῦνται, οὕτω δ' οὐκ ἀναιροῦνται αἱ προτάσεις.

5 Φανερὸν οὖν διὰ τῶν εἰρημένων πῶς ἀντιστρεφομένου

τοῦ συμπεράσματος ἐν ἑκάστῳ σχήματι γίνεται συλλογισμός,

καὶ πότ' ἐναντίος τῇ προτάσει καὶ πότ' ἀντικείμενος,

καὶ ὅτι ἐν μὲν τῷ πρώτῳ σχήματι διὰ τοῦ μέσου καὶ τοῦ

ἐσχάτου γίνονται οἱ συλλογισμοί, καὶ ἡ μὲν πρὸς τῷ ἐλάττονι

10 ἄκρῳ ἀεὶ διὰ τοῦ μέσου ἀναιρεῖται, ἡ δὲ πρὸς τῷ μείζονι

διὰ τοῦ ἐσχάτου· ἐν δὲ τῷ δευτέρῳ διὰ τοῦ πρώτου καὶ

τοῦ ἐσχάτου, ἡ μὲν πρὸς τῷ ἐλάττονι ἄκρῳ ἀεὶ διὰ τοῦ

πρώτου σχήματος, ἡ δὲ πρὸς τῷ μείζονι διὰ τοῦ ἐσχάτου·

ἐν δὲ τῷ τρίτῳ διὰ τοῦ πρώτου καὶ διὰ τοῦ μέσου, καὶ ἡ

15 μὲν πρὸς τῷ μείζονι διὰ τοῦ πρώτου ἀεί, ἡ δὲ πρὸς τῷ

ἐλάττονι διὰ τοῦ μέσου.

1If A belongs to some B and B to some C, no syllogism results: nor yet if A belongs to some B, and to no C. Thus in one way the premisses are refuted, in the other way they are not.
5From what has been said it is clear how a syllogism results in each figure when the conclusion is converted; when a result contrary to the premiss, and when a result contradictory to the premiss, is obtained. It is clear that in the first figure the syllogisms are formed through the middle and the last figures, and 10the premiss which concerns the minor extreme is alway refuted through the middle figure, the premiss which concerns the major through the last figure. In the second figure syllogisms proceed through the first and the last figures, and the premiss which concerns the minor extreme is always refuted through the first figure, the premiss which concerns the major extreme through the last. In the third figure the refutation proceeds through the first and the middle figures; 15the premiss which concerns the major is always refuted through the first figure, the premiss which concerns the minor through the middle figure.

Book 2,Chapter 11 (61a17–62a19)

Τί μὲν οὖν ἐστὶ τὸ ἀντιστρέφειν καὶ πῶς ἐν ἑκάστῳ

σχήματι καὶ τίς γίνεται συλλογισμός, φανερόν. ὁ δὲ διὰ

τοῦ ἀδυνάτου συλλογισμὸς δείκνυται μὲν ὅταν ἡ ἀντίφασις

20 τεθῇ τοῦ συμπεράσματος καὶ προσληφθῇ ἄλλη πρότασις,

γίνεται δ' ἐν ἅπασι τοῖς σχήμασιν· ὅμοιον γάρ ἐστι

τῇ ἀντιστροφῇ, πλὴν διαφέρει τοσοῦτον ὅτι ἀντιστρέφεται

μὲν γεγενημένου συλλογισμοῦ καὶ εἰλημμένων ἀμφοῖν τῶν

προτάσεων, ἀπάγεται δ' εἰς ἀδύνατον οὐ προομολογηθέντος

25 τοῦ ἀντικειμένου πρότερον, ἀλλὰ φανεροῦ ὄντος ὅτι ἀληθές.

οἱ δ' ὅροι ὁμοίως ἔχουσιν ἐν ἀμφοῖν, καὶ ἡ αὐτὴ λῆψις

ἀμφοτέρων. οἷον εἰ τὸ Α τῷ Β παντὶ ὑπάρχει, μέσον δὲ

τὸ Γ, ἐὰν ὑποτεθῇ τὸ Α ἢ μὴ παντὶ ἢ μηδενὶ τῷ Β ὑπάρχειν,

τῷ δὲ Γ παντί, ὅπερ ἦν ἀληθές, ἀνάγκη τὸ Γ τῷ

30 Β ἢ μηδενὶ ἢ μὴ παντὶ ὑπάρχειν. τοῦτο δ' ἀδύνατον, ὥστε

ψεῦδος τὸ ὑποτεθέν· ἀληθὲς ἄρα τὸ ἀντικείμενον. ὁμοίως δὲ

καὶ ἐπὶ τῶν ἄλλων σχημάτων· ὅσα γὰρ ἀντιστροφὴν δέχεται,

καὶ τὸν διὰ τοῦ ἀδυνάτου συλλογισμόν.

Τὰ μὲν οὖν ἄλλα προβλήματα πάντα δείκνυται διὰ

35 τοῦ ἀδυνάτου ἐν ἅπασι τοῖς σχήμασι, τὸ δὲ καθόλου κατηγορικὸν

ἐν μὲν τῷ μέσῳ καὶ τῷ τρίτῳ δείκνυται, ἐν δὲ

τῷ πρώτῳ οὐ δείκνυται. ὑποκείσθω γὰρ τὸ Α τῷ Β μὴ παντὶ

ἢ μηδενὶ ὑπάρχειν, καὶ προσειλήφθω ἄλλη πρότασις ὁποτερωθενοῦν,

εἴτε τῷ Α παντὶ ὑπάρχειν τὸ Γ εἴτε τὸ Β παντὶ

40 τῷ Δ· οὕτω γὰρ ἂν εἴη τὸ πρῶτον σχῆμα. εἰ μὲν οὖν ὑπόκειται

μὴ παντὶ ὑπάρχειν τὸ Α τῷ Β, οὐ γίνεται συλλογισμὸς

17It is clear then what conversion is, how it is effected in each figure, and what syllogism results. The syllogism per impossibile is proved when the contradictory of 20the conclusion stated and another premiss is assumed; it can be made in all the figures. For it resembles conversion, differing only in this: conversion takes place after a syllogism has been formed and both the premisses have been taken, but a reduction to the impossible takes place not because the contradictory has been 25agreed to already, but because it is clear that it is true. The terms are alike in both, and the premisses of both are taken in the same way. For example if A belongs to all B, C being middle, then if it is supposed that A does not belong to all B or belongs to no B, but to all C (which was admitted to be true), it follows that C belongs to 30no B or not to all B. But this is impossible: consequently the supposition is false: its contradictory then is true. Similarly in the other figures: for whatever moods admit of conversion admit also of the reduction per impossibile.
All the problems can be proved 35per impossibile in all the figures, excepting the universal affirmative, which is proved in the middle and third figures, but not in the first. Suppose that A belongs not to all B, or to no B, and take besides another premiss concerning either of the terms, viz. that C belongs to all A, or that 40B belongs to all D; thus we get the first figure. If then it is supposed that A does not belong to all B, no syllogism results whichever term the assumed premiss concerns; but if it is supposed that A belongs to no B, when the premiss BD is assumed as well we shall prove syllogistically what is false, but not the problem proposed. For if A belongs to no B, and B belongs to all D, A belongs to no D.

61b

1 ὁποτερωθενοῦν τῆς προτάσεως λαμβανομένης, εἰ δὲ

μηδενί, ὅταν μὲν ἡ Β Δ προσληφθῇ, συλλογισμὸς μὲν ἔσται

τοῦ ψεύδους, οὐ δείκνυται δὲ τὸ προκείμενον. εἰ γὰρ τὸ Α

μηδενὶ τῷ Β, τὸ δὲ Β παντὶ τῷ Δ, τὸ Α οὐδενὶ τῷ Δ.

5 τοῦτο δ' ἔστω ἀδύνατον· ψεῦδος ἄρα τὸ μηδενὶ τῷ Β τὸ Α

ὑπάρχειν. ἀλλ' οὐκ εἰ τὸ μηδενὶ ψεῦδος, τὸ παντὶ ἀληθές.

ἐὰν δ' ἡ Γ Α προσληφθῇ, οὐ γίνεται συλλογισμός, οὐδ'

ὅταν ὑποτεθῇ μὴ παντὶ τῷ Β τὸ Α ὑπάρχειν. ὥστε φανερὸν

ὅτι τὸ παντὶ ὑπάρχειν οὐ δείκνυται ἐν τῷ πρώτῳ σχήματι

10 διὰ τοῦ ἀδυνάτου. Τὸ δέ γε τινὶ καὶ τὸ μηδενὶ καὶ μὴ παντὶ

δείκνυται. ὑποκείσθω γὰρ τὸ Α μηδενὶ τῷ Β ὑπάρχειν, τὸ

δὲ Β εἰλήφθω παντὶ ἢ τινὶ τῷ Γ. οὐκοῦν ἀνάγκη τὸ Α μηδενὶ

ἢ μὴ παντὶ τῷ Γ ὑπάρχειν. τοῦτο δ' ἀδύνατον—ἔστω

γὰρ ἀληθὲς καὶ φανερὸν ὅτι παντὶ ὑπάρχει τῷ Γ τὸ Α—

15 ὥστ' εἰ τοῦτο ψεῦδος, ἀνάγκη τὸ Α τινὶ τῷ Β ὑπάρχειν. ἐὰν

δὲ πρὸς τῷ Α ληφθῇ ἡ ἑτέρα πρότασις, οὐκ ἔσται συλλογισμός.

οὐδ' ὅταν τὸ ἐναντίον τῷ συμπεράσματι ὑποτεθῇ,

οἷον τὸ τινὶ μὴ ὑπάρχειν. φανερὸν οὖν ὅτι τὸ ἀντικείμενον ὑποθετέον.

Πάλιν ὑποκείσθω τὸ Α τινὶ τῷ Β ὑπάρχειν, εἰλήφθω

20 δὲ τὸ Γ παντὶ τῷ Α. ἀνάγκη οὖν τὸ Γ τινὶ τῷ Β

ὑπάρχειν. τοῦτο δ' ἔστω ἀδύνατον, ὥστε ψεῦδος τὸ ὑποτεθέν.

εἰ δ' οὕτως, ἀληθὲς τὸ μηδενὶ ὑπάρχειν. ὁμοίως δὲ καὶ εἰ

στερητικὸν ἐλήφθη τὸ Γ Α. εἰ δ' ἡ πρὸς τῷ Β εἴληπται πρότασις,

οὐκ ἔσται συλλογισμός. ἐὰν δὲ τὸ ἐναντίον ὑποτεθῇ,

25 συλλογισμὸς μὲν ἔσται καὶ τὸ ἀδύνατον, οὐ δείκνυται δὲ τὸ

προτεθέν. ὑποκείσθω γὰρ παντὶ τῷ Β τὸ Α ὑπάρχειν, καὶ

τὸ Γ τῷ Α εἰλήφθω παντί. οὐκοῦν ἀνάγκη τὸ Γ παντὶ τῷ

Β ὑπάρχειν. τοῦτο δ' ἀδύνατον, ὥστε ψεῦδος τὸ παντὶ τῷ Β

τὸ Α ὑπάρχειν. ἀλλ' οὔπω γε ἀναγκαῖον, εἰ μὴ παντί,

30 μηδενὶ ὑπάρχειν. ὁμοίως δὲ καὶ εἰ πρὸς τῷ Β ληφθείη ἡ

ἑτέρα πρότασις· συλλογισμὸς μὲν γὰρ ἔσται καὶ τὸ ἀδύνατον,

οὐκ ἀναιρεῖται δ' ἡ ὑπόθεσις· ὥστε τὸ ἀντικείμενον

ὑποθετέον. Πρὸς δὲ τὸ μὴ παντὶ δεῖξαι ὑπάρχον τῷ Β τὸ

Α, ὑποθετέον παντὶ ὑπάρχειν· εἰ γὰρ τὸ Α παντὶ τῷ Β

35 καὶ τὸ Γ παντὶ τῷ Α, τὸ Γ παντὶ τῷ Β, ὥστ' εἰ τοῦτο

ἀδύνατον, ψεῦδος τὸ ὑποτεθέν. ὁμοίως δὲ καὶ εἰ πρὸς τῷ Β

ἐλήφθη ἡ ἑτέρα πρότασις. καὶ εἰ στερητικὸν ἦν τὸ Γ Α, ὡςαύτως·

καὶ γὰρ οὕτω γίνεται συλλογισμός. ἐὰν δὲ πρὸς τῷ

Β ᾖ τὸ στερητικόν, οὐδὲν δείκνυται. ἐὰν δὲ μὴ παντὶ ἀλλὰ

40 τινὶ ὑπάρχειν ὑποτεθῇ, οὐ δείκνυται ὅτι οὐ παντὶ ἀλλ' ὅτι

οὐδενί. εἰ γὰρ τὸ Α τινὶ τῷ Β, τὸ δὲ Γ παντὶ τῷ Α, τινὶ

1Let this be impossible: it is false then A belongs to no B. But the universal affirmative is not necessarily true if the universal negative is false. But if the premiss CA is assumed as well, no syllogism results, nor does it do so when it is supposed that A does not belong to all B. Consequently it is clear that the universal affirmative cannot be proved 10in the first figure per impossibile.
But the particular affirmative and the universal and particular negatives can all be proved. Suppose that A belongs to no B, and let it have been assumed that B belongs to all or to some C. Then it is necessary that A should belong to no C or not to all C. But this is impossible (for let it be true and clear that A belongs to all C): 15consequently if this is false, it is necessary that A should belong to some B. But if the other premiss assumed relates to A, no syllogism will be possible. Nor can a conclusion be drawn when the contrary of the conclusion is supposed, e.g. that A does not belong to some B. Clearly then we must suppose the contradictory.
Again suppose that A belongs to some B, and let it have been assumed that 20C belongs to all A. It is necessary then that C should belong to some B. But let this be impossible, so that the supposition is false: in that case it is true that A belongs to no B. We may proceed in the same way if the proposition CA has been taken as negative. But if the premiss assumed concerns B, no syllogism will be possible. If the contrary is supposed, 25we shall have a syllogism and an impossible conclusion, but the problem in hand is not proved. Suppose that A belongs to all B, and let it have been assumed that C belongs to all A. It is necessary then that C should belong to all B. But this is impossible, so that it is false that A belongs to all B. But we have not yet shown it to be necessary that A belongs to no B, 30if it does not belong to all B. Similarly if the other premiss taken concerns B; we shall have a syllogism and a conclusion which is impossible, but the hypothesis is not refuted. Therefore it is the contradictory that we must suppose.
To prove that A does not belong to all B, we must suppose that it belongs to all B: for if A belongs to all B, 35and C to all A, then C belongs to all B; so that if this is impossible, the hypothesis is false. Similarly if the other premiss assumed concerns B. The same results if the original proposition CA was negative: for thus also we get a syllogism. But if the negative proposition concerns B, nothing is proved. If the hypothesis is that A belongs not to all 40but to some B, it is not proved that A belongs not to all B, but that it belongs to no B. For if A belongs to some B, and C to all A, then C will belong to some B. If then this is impossible, it is false that A belongs to some B; consequently it is true that A belongs to no B.

62a

1 τῷ Β τὸ Γ ὑπάρξει. εἰ οὖν τοῦτ' ἀδύνατον, ψεῦδος τὸ τινὶ

ὑπάρχειν τῷ Β τὸ Α, ὥστ' ἀληθὲς τὸ μηδενί. τούτου δὲ

δειχθέντος προσαναιρεῖται τὸ ἀληθές· τὸ γὰρ Α τῷ Β τινὶ

μὲν ὑπῆρχε, τινὶ δ' οὐχ ὑπῆρχεν. ἔτι οὐδὲν παρὰ τὴν ὑπόθεσιν

5 συμβαίνει [τὸ] ἀδύνατον· ψεῦδος γὰρ ἂν εἴη, εἴπερ ἐξ

ἀληθῶν μὴ ἔστι ψεῦδος συλλογίσασθαι· νῦν δ' ἐστὶν ἀληθές·

ὑπάρχει γὰρ τὸ Α τινὶ τῷ Β. ὥστ' οὐχ ὑποθετέον τινὶ ὑπάρχειν,

ἀλλὰ παντί. ὁμοίως δὲ καὶ εἰ τινὶ μὴ ὑπάρχον τῷ Β

τὸ Α δεικνύοιμεν· εἰ γὰρ ταὐτὸ τὸ τινὶ μὴ ὑπάρχειν καὶ

10 μὴ παντὶ ὑπάρχειν, ἡ αὐτὴ ἀμφοῖν ἀπόδειξις.

Φανερὸν οὖν ὅτι οὐ τὸ ἐναντίον ἀλλὰ τὸ ἀντικείμενον

ὑποθετέον ἐν ἅπασι τοῖς συλλογισμοῖς. οὕτω γὰρ τό τε ἀναγκαῖον

ἔσται καὶ τὸ ἀξίωμα ἔνδοξον. εἰ γὰρ κατὰ παντὸς ἡ

φάσις ἢ ἡ ἀπόφασις, δειχθέντος ὅτι οὐχ ἡ ἀπόφασις,

15 ἀνάγκη τὴν κατάφασιν ἀληθεύεσθαι. πάλιν εἰ μὴ τίθησιν

ἀληθεύεσθαι τὴν κατάφασιν, ἔνδοξον τὸ ἀξιῶσαι τὴν ἀπόφασιν.

τὸ δ' ἐναντίον οὐδετέρως ἁρμόττει ἀξιοῦν· οὔτε γὰρ

ἀναγκαῖον, εἰ τὸ μηδενὶ ψεῦδος, τὸ παντὶ ἀληθές, οὔτ' ἔνδοξον

ὡς εἰ θάτερον ψεῦδος, ὅτι θάτερον ἀληθές.

1But if this is proved, the truth is refuted as well; for the original conclusion was that A belongs to some B, and does not belong to some B. Further the impossible does not result from the hypothesis: 5for then the hypothesis would be false, since it is impossible to draw a false conclusion from true premisses: but in fact it is true: for A belongs to some B. Consequently we must not suppose that A belongs to some B, but that it belongs to all B. Similarly if we should be proving that A does not belong to some B: for if 'not to belong to some' and 'to belong not to all' 10have the same meaning, the demonstration of both will be identical.
It is clear then that not the contrary but the contradictory ought to be supposed in all the syllogisms. For thus we shall have necessity of inference, and the claim we make is one that will be generally accepted. For if of everything one or other of two contradictory statements holds good, then if it is proved that the negation does not hold, 15the affirmation must be true. Again if it is not admitted that the affirmation is true, the claim that the negation is true will be generally accepted. But in neither way does it suit to maintain the contrary: for it is not necessary that if the universal negative is false, the universal affirmative should be true, nor is it generally accepted that if the one is false the other is true.

Book 2,Chapter 12 (62a20–62b4)

20 Φανερὸν οὖν ὅτι ἐν τῷ πρώτῳ σχήματι τὰ μὲν ἄλλα

προβλήματα πάντα δείκνυται διὰ τοῦ ἀδυνάτου, τὸ δὲ καθόλου

καταφατικὸν οὐ δείκνυται. ἐν δὲ τῷ μέσῳ καὶ τῷ

ἐσχάτῳ καὶ τοῦτο δείκνυται. κείσθω γὰρ τὸ Α μὴ παντὶ

τῷ Β ὑπάρχειν, εἰλήφθω δὲ τῷ Γ παντὶ ὑπάρχειν τὸ Α.

25 οὐκοῦν εἰ τῷ μὲν Β μὴ παντί, τῷ δὲ Γ παντί, οὐ παντὶ

τῷ Β τὸ Γ. τοῦτο δ' ἀδύνατον· ἔστω γὰρ φανερὸν ὅτι παντὶ

τῷ Β ὑπάρχει τὸ Γ, ὥστε ψεῦδος τὸ ὑποκείμενον. ἀληθὲς

ἄρα τὸ παντὶ ὑπάρχειν. ἐὰν δὲ τὸ ἐναντίον ὑποτεθῇ, συλλογισμὸς

μὲν ἔσται καὶ τὸ ὀδύνατον, οὐ μὴν δείκνυται τὸ

30 προτεθέν. εἰ γὰρ τὸ Α μηδενὶ τῷ Β, τῷ δὲ Γ παντί, οὐδενὶ

τῷ Β τὸ Γ. τοῦτο δ' ἀδύνατον, ὥστε ψεῦδος τὸ μηδενὶ ὑπάρχειν.

ἀλλ' οὐκ εἰ τοῦτο ψεῦδος, τὸ παντὶ ἀληθές. ὅτι δὲ

τινὶ τῷ Β ὑπάρχει τὸ Α, ὑποκείσθω τὸ Α μηδενὶ τῷ Β

ὑπάρχειν, τῷ δὲ Γ παντὶ ὑπαρχέτω. ἀνάγκη οὖν τὸ Γ μηδενὶ

35 τῷ Β. ὥστ' εἰ τοῦτ' ἀδύνατον, ἀνάγκη τὸ Α τινὶ τῷ Β

ὑπάρχειν. ἐὰν δ' ὑποτεθῇ τινὶ μὴ ὑπάρχειν, ταὐτ' ἔσται

ἅπερ ἐπὶ τοῦ πρώτου σχήματος. πάλιν ὑποκείσθω τὸ Α τινὶ

τῷ Β ὑπάρχειν, τῷ δὲ Γ μηδενὶ ὑπαρχέτω. ἀνάγκη οὖν

τὸ Γ τινὶ τῷ Β μὴ ὑπάρχειν. ἀλλὰ παντὶ ὑπῆρχεν, ὥστε

40 ψεῦδος τὸ ὑποτεθέν· οὐδενὶ ἄρα τῷ Β τὸ Α ὑπάρξει. ὅτι

δ' οὐ παντὶ τὸ Α τῷ Β, ὑποκείσθω παντὶ ὑπάρχειν, τῷ

20It is clear then that in the first figure all problems except the universal affirmative are proved per impossibile. But in the middle and the last figures this also is proved. Suppose that A does not belong to all B, and let it have been assumed that A belongs to all C. 25If then A belongs not to all B, but to all C, C will not belong to all B. But this is impossible (for suppose it to be clear that C belongs to all B): consequently the hypothesis is false. It is true then that A belongs to all B. But if the contrary is supposed, we shall have a syllogism and a result which is impossible: but 30the problem in hand is not proved. For if A belongs to no B, and to all C, C will belong to no B. This is impossible; so that it is false that A belongs to no B. But though this is false, it does not follow that it is true that A belongs to all B.
When A belongs to some B, suppose that A belongs to no B, and let A belong to all C. It is necessary then that C should belong to no B. 35Consequently, if this is impossible, A must belong to some B. But if it is supposed that A does not belong to some B, we shall have the same results as in the first figure.
Again suppose that A belongs to some B, and let A belong to no C. It is necessary then that C should not belong to some B. But originally it belonged to all B, 40consequently the hypothesis is false: A then will belong to no B.

62b

1 δὲ Γ μηδενί. ἀνάγκη οὖν τὸ Γ μηδενὶ τῷ Β ὑπάρχειν. τοῦτο

δ' ἀδύνατον, ὥστ' ἀληθὲς τὸ μὴ παντὶ ὑπάρχειν. φανερὸν

οὖν ὅτι πάντες οἱ συλλογισμοὶ γίνονται διὰ τοῦ μέσου σχήματος.

1When A does not belong to an B, suppose it does belong to all B, and to no C. It is necessary then that C should belong to no B. But this is impossible: so that it is true that A does not belong to all B. It is clear then that all the syllogisms can be formed in the middle figure.

Book 2,Chapter 13 (62b5–28)

5 Ὁμοίως δὲ καὶ διὰ τοῦ ἐσχάτου. κείσθω γὰρ τὸ Α

τινὶ τῷ Β μὴ ὑπάρχειν, τὸ δὲ Γ παντί· τὸ ἄρα Α τινὶ τῷ

Γ οὐχ ὑπάρχει. εἰ οὖν τοῦτ' ἀδύνατον, ψεῦδος τὸ τινὶ μὴ

ὑπάρχειν, ὥστ' ἀληθὲς τὸ παντί. ἐὰν δ' ὑποτεθῇ μηδενὶ

ὑπάρχειν, συλλογισμὸς μὲν ἔσται καὶ τὸ ἀδύνατον, οὐ δείκνυται

10 δὲ τὸ προτεθέν· ἐὰν γὰρ τὸ ἐναντίον ὑποτεθῇ, ταὐτ'

ἔσται ἅπερ ἐπὶ τῶν πρότερον. ἀλλὰ πρὸς τὸ τινὶ ὑπάρχειν

αὕτη ληπτέα ἡ ὑπόθεσις. εἰ γὰρ τὸ Α μηδενὶ τῷ Β, τὸ δὲ

Γ τινὶ τῷ Β, τὸ Α οὐ παντὶ τῷ Γ. εἰ οὖν τοῦτο ψεῦδος,

ἀληθὲς τὸ Α τινὶ τῷ Β ὑπάρχειν. ὅτι δ' οὐδενὶ τῷ Β ὑπάρχει

15 τὸ Α, ὑποκείσθω τινὶ ὑπάρχειν, εἰλήφθω δὲ καὶ τὸ Γ

παντὶ τῷ Β ὑπάρχον. οὐκοῦν ἀνάγκη τῷ Γ τινὶ τὸ Α ὑπάρχειν.

ἀλλ' οὐδενὶ ὑπῆρχεν, ὥστε ψεῦδος τὸ τινὶ τῷ Β ὑπάρχειν

τὸ Α. ἐὰν δ' ὑποτεθῇ παντὶ τῷ Β ὑπάρχειν τὸ Α, οὐ

δείκνυται τὸ προτεθέν, ἀλλὰ πρὸς τὸ μὴ παντὶ ὑπάρχειν

20 αὕτη ληπτέα ἡ ὑπόθεσις. εἰ γὰρ τὸ Α παντὶ τῷ Β καὶ τὸ

Γ παντὶ τῷ Β, τὸ Α ὑπάρχει τινὶ τῷ Γ. τοῦτο δὲ οὐκ ἦν,

ὥστε ψεῦδος τὸ παντὶ ὑπάρχειν. εἰ δ' οὕτως, ἀληθὲς τὸ μὴ

παντί. ἐὰν δ' ὑποτεθῇ τινὶ ὑπάρχειν, ταὐτ' ἔσται ἃ καὶ

ἐπὶ τῶν προειρημένων.

25 Φανερὸν οὖν ὅτι ἐν ἅπασι τοῖς διὰ τοῦ ἀδυνάτου συλλογισμοῖς

τὸ ἀντικείμενον ὑποθετέον. δῆλον δὲ καὶ ὅτι ἐν τῷ

μέσῳ σχήματι δείκνυταί πως τὸ καταφατικὸν καὶ ἐν τῷ

ἐσχάτῳ τὸ καθόλου.

5Similarly they can all be formed in the last figure. Suppose that A does not belong to some B, but C belongs to all B: then A does not belong to some C. If then this is impossible, it is false that A does not belong to some B; so that it is true that A belongs to all B. But if it is supposed that A belongs to no B, we shall have a syllogism and a conclusion which is impossible: but the problem in hand is not proved: 10for if the contrary is supposed, we shall have the same results as before.
But to prove that A belongs to some B, this hypothesis must be made. If A belongs to no B, and C to some B, A will belong not to all C. If then this is false, it is true that A belongs to some B.
When A belongs to no B, 15suppose A belongs to some B, and let it have been assumed that C belongs to all B. Then it is necessary that A should belong to some C. But ex hypothesi it belongs to no C, so that it is false that A belongs to some B. But if it is supposed that A belongs to all B, the problem is not proved.
But this hypothesis must be made if we are prove that A belongs not to all B. 20For if A belongs to all B and C to some B, then A belongs to some C. But this we assumed not to be so, so it is false that A belongs to all B. But in that case it is true that A belongs not to all B. If however it is assumed that A belongs to some B, we shall have the same result as before.
25It is clear then that in all the syllogisms which proceed per impossibile the contradictory must be assumed. And it is plain that in the middle figure an affirmative conclusion, and in the last figure a universal conclusion, are proved in a way.

Book 2,Chapter 14 (62b29–63b21)

Διαφέρει δ' ἡ εἰς τὸ ἀδύνατον ἀπόδειξις τῆς δεικτικῆς

30 τῷ τιθέναι ὃ βούλεται ἀναιρεῖν ἀπάγουσα εἰς ὁμολογούμενον

ψεῦδος· ἡ δὲ δεικτικὴ ἄρχεται ἐξ ὁμολογουμένων θέσεων.

λαμβάνουσι μὲν οὖν ἀμφότεραι δύο προτάσεις

ὁμολογουμένας· ἀλλ' ἡ μὲν ἐξ ὧν ὁ συλλογισμός, ἡ δὲ

μίαν μὲν τούτων, μίαν δὲ τὴν ἀντίφασιν τοῦ συμπεράσματος.

35 καὶ ἔνθα μὲν οὐκ ἀνάγκη γνώριμον εἶναι τὸ συμπέρασμα,

οὐδὲ προϋπολαμβάνειν ὡς ἔστιν ἢ οὔ· ἔνθα δὲ

ἀνάγκη ὡς οὐκ ἔστιν. διαφέρει δ' οὐδὲν φάσιν ἢ ἀπόφασιν

εἶναι τὸ συμπέρασμα, ἀλλ' ὁμοίως ἔχει περὶ ἀμφοῖν. Ἅπαν

δὲ τὸ δεικτικῶς περαινόμενον καὶ διὰ τοῦ ἀδυνάτου δειχθήσεται,

40 καὶ τὸ διὰ τοῦ ἀδυνάτου δεικτικῶς διὰ τῶν αὐτῶν ὅρων

[οὐκ ἐν τοῖς αὐτοῖς δὲ σχήμασιν]. ὅταν μὲν γὰρ ὁ συλλογισμὸς

29Demonstration per impossibile differs from ostensive proof 30in that it posits what it wishes to refute by reduction to a statement admitted to be false; whereas ostensive proof starts from admitted positions. Both, indeed, take two premisses that are admitted, but the latter takes the premisses from which the syllogism starts, the former takes one of these, along with the contradictory of the original conclusion. 35Also in the ostensive proof it is not necessary that the conclusion should be known, nor that one should suppose beforehand that it is true or not: in the other it is necessary to suppose beforehand that it is not true. It makes no difference whether the conclusion is affirmative or negative; the method is the same in both cases. Everything which is concluded ostensively can be proved per impossibile, 40and that which is proved per impossibile can be proved ostensively, through the same terms.

63a

1 ἐν τῷ πρώτῳ σχήματι γένηται, τὸ ἀληθὲς ἔσται ἐν

τῷ μέσῳ ἢ τῷ ἐσχάτῳ, τὸ μὲν στερητικὸν ἐν τῷ μέσῳ, τὸ

δὲ κατηγορικὸν ἐν τῷ ἐσχάτῳ. ὅταν δ' ἐν τῷ μέσῳ ὁ

συλλογισμός, τὸ ἀληθὲς ἐν τῷ πρώτῳ ἐπὶ πάντων τῶν

5 προβλημάτων. ὅταν δ' ἐν τῷ ἐσχάτῳ ὁ συλλογισμός, τὸ

ἀληθὲς ἐν τῷ πρώτῳ καὶ τῷ μέσῳ, τὰ μὲν καταφατικὰ

ἐν τῷ πρώτῳ, τὰ δὲ στερητικὰ ἐν τῷ μέσῳ. ἔστω γὰρ δεδειγμένον

τὸ Α μηδενὶ ἢ μὴ παντὶ τῷ Β διὰ τοῦ πρώτου σχήματος.

οὐκοῦν ἡ μὲν ὑπόθεσις ἦν τινὶ τῷ Β ὑπάρχειν τὸ Α,

10 τὸ δὲ Γ ἐλαμβάνετο τῷ μὲν Α παντὶ ὑπάρχειν, τῷ δὲ Β

οὐδενί· οὕτω γὰρ ἐγίνετο ὁ συλλογισμὸς καὶ τὸ ἀδύνατον.

τοῦτο δὲ τὸ μέσον σχῆμα, εἰ τὸ Γ τῷ μὲν Α παντὶ τῷ δὲ

Β μηδενὶ ὑπάρχει. καὶ φανερὸν ἐκ τούτων ὅτι οὐδενὶ τῷ Β

ὑπάρχει τὸ Α. ὁμοίως δὲ καὶ εἰ μὴ παντὶ δέδεικται ὑπάρχον.

15 ἡ μὲν γὰρ ὑπόθεσίς ἐστι παντὶ ὑπάρχειν, τὸ δὲ Γ

ἐλαμβάνετο τῷ μὲν Α παντί, τῷ δὲ Β οὐ παντί. καὶ εἰ

στερητικὸν λαμβάνοιτο τὸ Γ Α, ὡσαύτως· καὶ γὰρ οὕτω γίνεται

τὸ μέσον σχῆμα. πάλιν δεδείχθω τινὶ ὑπάρχον τῷ

Β τὸ Α. ἡ μὲν οὖν ὑπόθεσις μηδενὶ ὑπάρχειν, τὸ δὲ Β

20 ἐλαμβάνετο παντὶ τῷ Γ ὑπάρχειν καὶ τὸ Α ἢ παντὶ ἢ τινὶ

τῷ Γ· οὕτω γὰρ ἔσται τὸ ἀδύνατον. τοῦτο δὲ τὸ ἔσχατον

σχῆμα, εἰ τὸ Α καὶ τὸ Β παντὶ τῷ Γ. καὶ φανερὸν ἐκ

τούτων ὅτι ἀνάγκη τὸ Α τινὶ τῷ Β ὑπάρχειν. ὁμοίως δὲ

καὶ εἰ τινὶ τῷ Γ ληφθείη ὑπάρχον τὸ Β ἢ τὸ Α.

25 Πάλιν ἐν τῷ μέσῳ σχήματι δεδείχθω τὸ Α παντὶ τῷ

Β ὑπάρχον. οὐκοῦν ἡ μὲν ὑπόθεσις ἦν μὴ παντὶ τῷ Β τὸ

Α ὑπάρχειν, εἴληπται δὲ τὸ Α παντὶ τῷ Γ καὶ τὸ Γ παντὶ

τῷ Β· οὕτω γὰρ ἔσται τὸ ἀδύνατον. τοῦτο δὲ τὸ πρῶτον

σχῆμα, τὸ Α παντὶ τῷ Γ καὶ τὸ Γ παντὶ τῷ Β. ὁμοίως

30 δὲ καὶ εἰ τινὶ δέδεικται ὑπάρχον· ἡ μὲν γὰρ ὑπόθεσις ἦν

μηδενὶ τῷ Β τὸ Α ὑπάρχειν, εἴληπται δὲ τὸ Α παντὶ τῷ

Γ καὶ τὸ Γ τινὶ τῷ Β. εἰ δὲ στερητικὸς ὁ συλλογισμός, ἡ

μὲν ὑπόθεσις τὸ Α τινὶ τῷ Β ὑπάρχειν, εἴληπται δὲ τὸ Α

μηδενὶ τῷ Γ καὶ τὸ Γ παντὶ τῷ Β, ὥστε γίνεται τὸ πρῶτον

35 σχῆμα. καὶ εἰ μὴ καθόλου ὁ συλλογισμός, ἀλλὰ τὸ

Α τινὶ τῷ Β δέδεικται μὴ ὑπάρχειν, ὡσαύτως. ὑπόθεσις

μὲν γὰρ παντὶ τῷ Β τὸ Α ὑπάρχειν, εἴληπται δὲ τὸ Α

μηδενὶ τῷ Γ καὶ τὸ Γ τινὶ τῷ Β· οὕτω γὰρ τὸ πρῶτον

σχῆμα.

40 Πάλιν ἐν τῷ τρίτῳ σχήματι δεδείχθω τὸ Α παντὶ τῷ

Β ὑπάρχειν. οὐκοῦν ἡ μὲν ὑπόθεσις ἦν μὴ παντὶ τῷ Β τὸ

1Whenever the syllogism is formed in the first figure, the truth will be found in the middle or the last figure, if negative in the middle, if affirmative in the last. Whenever the syllogism is formed in the middle figure, the truth will be found in the first, whatever the problem may be. 5Whenever the syllogism is formed in the last figure, the truth will be found in the first and middle figures, if affirmative in first, if negative in the middle. Suppose that A has been proved to belong to no B, or not to all B, through the first figure. Then the hypothesis must have been that A belongs to some B, and the original premisses 10that C belongs to all A and to no B. For thus the syllogism was made and the impossible conclusion reached. But this is the middle figure, if C belongs to all A and to no B. And it is clear from these premisses that A belongs to no B. Similarly if has been proved not to belong to all B. 15For the hypothesis is that A belongs to all B; and the original premisses are that C belongs to all A but not to all B. Similarly too, if the premiss CA should be negative: for thus also we have the middle figure. Again suppose it has been proved that A belongs to some B. The hypothesis here is that is that A belongs to no B; and the original premisses 20that B belongs to all C, and A either to all or to some C: for in this way we shall get what is impossible. But if A and B belong to all C, we have the last figure. And it is clear from these premisses that A must belong to some B. Similarly if B or A should be assumed to belong to some C.
25Again suppose it has been proved in the middle figure that A belongs to all B. Then the hypothesis must have been that A belongs not to all B, and the original premisses that A belongs to all C, and C to all B: for thus we shall get what is impossible. But if A belongs to all C, and C to all B, we have the first figure. 30Similarly if it has been proved that A belongs to some B: for the hypothesis then must have been that A belongs to no B, and the original premisses that A belongs to all C, and C to some B. If the syllogism is negative, the hypothesis must have been that A belongs to some B, and the original premisses that A belongs to no C, and C to all B, so that the first figure results. 35If the syllogism is not universal, but proof has been given that A does not belong to some B, we may infer in the same way. The hypothesis is that A belongs to all B, the original premisses that A belongs to no C, and C belongs to some B: for thus we get the first figure.
40Again suppose it has been proved in the third figure that A belongs to all B.

63b

1 Α ὑπάρχειν, εἴληπται δὲ τὸ Γ παντὶ τῷ Β καὶ τὸ Α παντὶ

τῷ Γ· οὕτω γὰρ ἔσται τὸ ἀδύνατον. τοῦτο δὲ τὸ πρῶτον

σχῆμα. ὡσαύτως δὲ καὶ εἰ ἐπὶ τινὸς ἡ ἀπόδειξις· ἡ μὲν

γὰρ ὑπόθεσις μηδενὶ τῷ Β τὸ Α ὑπάρχειν, εἴληπται δὲ τὸ

5 Γ τινὶ τῷ Β καὶ τὸ Α παντὶ τῷ Γ. εἰ δὲ στερητικὸς ὁ συλλογισμός,

ὑπόθεσις μὲν τὸ Α τινὶ τῷ Β ὑπάρχειν, εἴληπται

δὲ τὸ Γ τῷ μὲν Α μηδενί, τῷ δὲ Β παντί· τοῦτο δὲ

τὸ μέσον σχῆμα. ὁμοίως δὲ καὶ εἰ μὴ καθόλου ἡ ἀπόδειξις.

ὑπόθεσις μὲν γὰρ ἔσται παντὶ τῷ Β τὸ Α ὑπάρχειν,

10 εἴληπται δὲ τὸ Γ τῷ μὲν Α μηδενί, τῷ δὲ Β τινί· τοῦτο δὲ

τὸ μέσον σχῆμα.

Φανερὸν οὖν ὅτι διὰ τῶν αὐτῶν ὅρων καὶ δεικτικῶς ἔστι

δεικνύναι τῶν προβλημάτων ἕκαστον [καὶ διὰ τοῦ ἀδυνάτου].

ὁμοίως δ' ἔσται καὶ δεικτικῶν ὄντων τῶν συλλογισμῶν εἰς

15 ἀδύνατον ἀπάγειν ἐν τοῖς εἰλημμένοις ὅροις, ὅταν ἡ ἀντικειμένη

πρότασις τῷ συμπεράσματι ληφθῇ. γίνονται γὰρ οἱ

αὐτοὶ συλλογισμοὶ τοῖς διὰ τῆς ἀντιστροφῆς, ὥστ' εὐθὺς

ἔχομεν καὶ τὰ σχήματα δι' ὧν ἕκαστον ἔσται. δῆλον οὖν ὅτι

πᾶν πρόβλημα δείκνυται κατ' ἀμφοτέρους τοὺς τρόπους,

20 διά τε τοῦ ἀδυνάτου καὶ δεικτικῶς, καὶ οὐκ ἐνδέχεται χωρίζεσθαι

τὸν ἕτερον.

1Then the hypothesis must have been that A belongs not to all B, and the original premisses that C belongs to all B, and A belongs to all C; for thus we shall get what is impossible. And the original premisses form the first figure. Similarly if the demonstration establishes a particular proposition: the hypothesis then must have been that A belongs to no B, and the original premisses that 5C belongs to some B, and A to all C. If the syllogism is negative, the hypothesis must have been that A belongs to some B, and the original premisses 10that C belongs to no A and to all B, and this is the middle figure. Similarly if the demonstration is not universal. The hypothesis will then be that A belongs to all B, the premisses that C belongs to no A and to some B: and this is the middle figure.
It is clear then that it is possible through the same terms to prove each of the problems ostensively as well. Similarly it will be possible if the syllogisms are ostensive 15to reduce them ad impossibile in the terms which have been taken, whenever the contradictory of the conclusion of the ostensive syllogism is taken as a premiss. For the syllogisms become identical with those which are obtained by means of conversion, so that we obtain immediately the figures through which each problem will be solved. It is clear then that every thesis can be proved in both ways, i.e. 20per impossibile and ostensively, and it is not possible to separate one method from the other.

Book 2,Chapter 15 (63b22–64b27)

Ἐν ποίῳ δὲ σχήματι ἔστιν ἐξ ἀντικειμένων προτάσεων

συλλογίσασθαι καὶ ἐν ποίῳ οὐκ ἔστιν, ὧδ' ἔσται φανερόν. λέγω

δ' ἀντικειμένας εἶναι προτάσεις κατὰ μὲν τὴν λέξιν τέτταρας,

25 οἷον τὸ παντὶ τῷ οὐδενί, καὶ τὸ παντὶ τῷ οὐ παντί, καὶ

τὸ τινὶ τῷ οὐδενί, καὶ τὸ τινὶ τῷ οὐ τινί, κατ' ἀλήθειαν δὲ

τρεῖς· τὸ γὰρ τινὶ τῷ οὐ τινὶ κατὰ τὴν λέξιν ἀντίκειται μόνον.

τούτων δ' ἐναντίας μὲν τὰς καθόλου, τὸ παντὶ τῷ μηδενὶ

ὑπάρχειν, οἷον τὸ πᾶσαν ἐπιστήμην εἶναι σπουδαίαν τῷ

30 μηδεμίαν εἶναι σπουδαίαν, τὰς δ' ἄλλας ἀντικειμένας.

Ἐν μὲν οὖν τῷ πρώτῳ σχήματι οὐκ ἔστιν ἐξ ἀντικειμένων

προτάσεων συλλογισμός, οὔτε καταφατικὸς οὔτε ἀποφατικός,

καταφατικὸς μὲν ὅτι ἀμφοτέρας δεῖ καταφατικὰς

εἶναι τὰς προτάσεις, αἱ δ' ἀντικείμεναι φάσις καὶ

35 ἀπόφασις, στερητικὸς δὲ ὅτι αἱ μὲν ἀντικείμεναι τὸ αὐτὸ

τοῦ αὐτοῦ κατηγοροῦσι καὶ ἀπαρνοῦνται, τὸ δ' ἐν τῷ πρώτῳ

μέσον οὐ λέγεται κατ' ἀμφοῖν, ἀλλ' ἐκείνου μὲν ἄλλο ἀπαρνεῖται,

αὐτὸ δὲ ἄλλου κατηγορεῖται· αὗται δ' οὐκ ἀντίκεινται.

40 Ἐν δὲ τῷ μέσῳ σχήματι καὶ ἐκ τῶν ἀντικειμένων καὶ

ἐκ τῶν ἐναντίων ἐνδέχεται γίγνεσθαι συλλογισμόν. ἔστω γὰρ

22In what figure it is possible to draw a conclusion from premisses which are opposed, and in what figure this is not possible, will be made clear in this way. Verbally four kinds of opposition are possible, viz. 25universal affirmative to universal negative, universal affirmative to particular negative, particular affirmative to universal negative, and particular affirmative to particular negative: but really there are only three: for the particular affirmative is only verbally opposed to the particular negative. Of the genuine opposites I call those which are universal contraries, the universal affirmative and the universal negative, e.g. 'every science is good', 30'no science is good'; the others I call contradictories.
In the first figure no syllogism whether affirmative or negative can be made out of opposed premisses: no affirmative syllogism is possible because both premisses must be affirmative, but opposites are, the one affirmative, the other negative: 35no negative syllogism is possible because opposites affirm and deny the same predicate of the same subject, and the middle term in the first figure is not predicated of both extremes, but one thing is denied of it, and it is affirmed of something else: but such premisses are not opposed.
40In the middle figure a syllogism can be made both oLcontradictories and of contraries.

64a

1 ἀγαθὸν μὲν ἐφ' οὗ Α, ἐπιστήμη δὲ ἐφ' οὗ Β καὶ Γ. εἰ δὴ

πᾶσαν ἐπιστήμην σπουδαίαν ἔλαβε καὶ μηδεμίαν, τὸ Α τῷ

Β παντὶ ὑπάρχει καὶ τῷ Γ οὐδενί, ὥστε τὸ Β τῷ Γ οὐδενί·

οὐδεμία ἄρα ἐπιστήμη ἐπιστήμη ἐστίν. ὁμοίως δὲ καὶ εἰ πᾶσαν

5 λαβὼν σπουδαίαν τὴν ἰατρικὴν μὴ σπουδαίαν ἔλαβε· τῷ

μὲν γὰρ Β παντὶ τὸ Α, τῷ δὲ Γ οὐδενί, ὥστε ἡ τὶς ἐπιστήμη

οὐκ ἔσται ἐπιστήμη. καὶ εἰ τῷ μὲν Γ παντὶ τὸ Α, τῷ δὲ Β

μηδενί, ἔστι δὲ τὸ μὲν Β ἐπιστήμη, τὸ δὲ Γ ἰατρική, τὸ δὲ

Α ὑπόληψις· οὐδεμίαν γὰρ ἐπιστήμην ὑπόληψιν λαβὼν εἴληφε

10 τινὰ εἶναι ὑπόληψιν. διαφέρει δὲ τοῦ πάλαι

τῷ ἐπὶ τῶν ὅρων ἀντιστρέφεσθαι· πρότερον μὲν γὰρ πρὸς τῷ

Β, νῦν δὲ πρὸς τῷ Γ τὸ καταφατικόν. καὶ ἂν ᾖ δὲ μὴ καθόλου

ἡ ἑτέρα πρότασις, ὡσαύτως· ἀεὶ γὰρ τὸ μέσον ἐστὶν

ὃ ἀπὸ θατέρου μὲν ἀποφατικῶς λέγεται, κατὰ θατέρου δὲ

15 καταφατικῶς. ὥστ' ἐνδέχεται τἀντικείμενα περαίνεσθαι,

πλὴν οὐκ ἀεὶ οὐδὲ πάντως, ἀλλ' ἐὰν οὕτως ἔχῃ τὰ ὑπὸ

τὸ μέσον ὥστ' ἢ ταὐτὰ εἶναι ἢ ὅλον πρὸς μέρος. ἄλλως δ'

ἀδύνατον· οὐ γὰρ ἔσονται οὐδαμῶς αἱ προτάσεις οὔτ' ἐναντίαι

οὔτ' ἀντικείμεναι.

20 Ἐν δὲ τῷ τρίτῳ σχήματι καταφατικὸς μὲν συλλογισμὸς

οὐδέποτ' ἔσται ἐξ ἀντικειμένων προτάσεων διὰ τὴν εἰρημένην

αἰτίαν καὶ ἐπὶ τοῦ πρώτου σχήματος, ἀποφατικὸς

δ' ἔσται, καὶ καθόλου καὶ μὴ καθόλου τῶν ὅρων ὄντων. ἔστω

γὰρ ἐπιστήμη ἐφ' οὗ τὸ Β καὶ Γ, ἰατρικὴ δ' ἐφ' οὗ Α. εἰ

25 οὖν λάβοι πᾶσαν ἰατρικὴν ἐπιστήμην καὶ μηδεμίαν ἰατρικὴν

ἐπιστήμην, τὸ Β παντὶ τῷ Α εἴληφε καὶ τὸ Γ οὐδενί, ὥστ'

ἔσται τις ἐπιστήμη οὐκ ἐπιστήμη. ὁμοίως δὲ καὶ ἂν μὴ καθόλου

ληφθῇ ἡ Β Α πρότασις· εἰ γάρ ἐστί τις ἰατρικὴ ἐπιστήμη

καὶ πάλιν μηδεμία ἰατρικὴ ἐπιστήμη, συμβαίνει ἐπιστήμην

30 τινὰ μὴ εἶναι ἐπιστήμην. εἰσὶ δὲ καθόλου μὲν τῶν

ὅρων λαμβανομένων ἐναντίαι αἱ προτάσεις, ἐὰν δ' ἐν μέρει

ἅτερος, ἀντικείμεναι.

Δεῖ δὲ κατανοεῖν ὅτι ἐνδέχεται μὲν οὕτω τὰ ἀντικείμενα

λαμβάνειν ὥσπερ εἴπομεν πᾶσαν ἐπιστήμην σπουδαίαν

35 εἶναι καὶ πάλιν μηδεμίαν, ἢ τινὰ μὴ σπουδαίαν·

ὅπερ οὐκ εἴωθε λανθάνειν. ἔστι δὲ δι' ἄλλων ἐρωτημάτων συλλογίσασθαι

θάτερον, ἢ ὡς ἐν τοῖς Τοπικοῖς ἐλέχθη λαβεῖν. ἐπεὶ

δὲ τῶν καταφάσεων αἱ ἀντιθέσεις τρεῖς, ἑξαχῶς συμβαίνει

τὰ ἀντικείμενα λαμβάνειν, ἢ παντὶ καὶ μηδενί, ἢ παντὶ

40 καὶ μὴ παντί, ἢ τινὶ καὶ μηδενί, καὶ τοῦτο ἀντιστρέψαι ἐπὶ

1Let A stand for good, let B and C stand for science. If then one assumes that every science is good, and no science is good, A belongs to all B and to no C, so that B belongs to no C: no science then is a science. Similarly if after taking '5every science is good' one took 'the science of medicine is not good'; for A belongs to all B but to no C, so that a particular science will not be a science. Again, a particular science will not be a science if A belongs to all C but to no B, and B is science, C medicine, and A supposition: for after taking 'no science is supposition', one has assumed that 10a particular science is supposition. This syllogism differs from the preceding because the relations between the terms are reversed: before, the affirmative statement concerned B, now it concerns C. Similarly if one premiss is not universal: for the middle term is always that which is stated negatively of one extreme, and affirmatively of the other. Consequently it is possible that contradictories may lead to a conclusion, 15though not always or in every mood, but only if the terms subordinate to the middle are such that they are either identical or related as whole to part. Otherwise it is impossible: for the premisses cannot anyhow be either contraries or contradictories.
20In the third figure an affirmative syllogism can never be made out of opposite premisses, for the reason given in reference to the first figure; but a negative syllogism is possible whether the terms are universal or not. Let B and C stand for science, A for medicine. If then 25one should assume that all medicine is science and that no medicine is science, he has assumed that B belongs to all A and C to no A, so that a particular science will not be a science. Similarly if the premiss BA is not assumed universally. For if some medicine is science and again no medicine is science, it 30results that some science is not science, The premisses are contrary if the terms are taken universally; if one is particular, they are contradictory.
We must recognize that it is possible to take opposites in the way we said, viz. 'all science is good' 35and 'no science is good' or 'some science is not good'. This does not usually escape notice. But it is possible to establish one part of a contradiction through other premisses, or to assume it in the way suggested in the Topics. Since there are three oppositions to affirmative statements, it follows that opposite statements may be assumed as premisses in six ways; we may have either universal affirmative and negative, or universal affirmative and particular negative, 40or particular affirmative and universal negative, and the relations between the terms may be reversed; e.g.

64b

1 τῶν ὅρων, οἷον τὸ Α παντὶ τῷ Β, τῷ δὲ Γ μηδενί, ἢ τῷ

Γ παντί, τῷ δὲ Β μηδενί, ἢ τῷ μὲν παντί, τῷ δὲ μὴ

παντί, καὶ πάλιν τοῦτο ἀντιστρέψαι κατὰ τοὺς ὅρους. ὁμοίως

δὲ καὶ ἐπὶ τοῦ τρίτου σχήματος. ὥστε φανερὸν ὁσαχῶς τε

5 καὶ ἐν ποίοις σχήμασιν ἐνδέχεται διὰ τῶν ἀντικειμένων προτάσεων

γενέσθαι συλλογισμόν.

Φανερὸν δὲ καὶ ὅτι ἐκ ψευδῶν μὲν ἔστιν ἀληθὲς συλλογίσασθαι,

καθάπερ εἴρηται πρότερον, ἐκ δὲ τῶν ἀντικειμένων

οὐκ ἔστιν· ἀεὶ γὰρ ἐναντίος ὁ συλλογισμὸς γίνεται τῷ

10 πράγματι, οἷον εἰ ἔστιν ἀγαθόν, μὴ εἶναι ἀγαθόν, ἢ εἰ ζῷον,

μὴ ζῷον, διὰ τὸ ἐξ ἀντιφάσεως εἶναι τὸν συλλογισμὸν καὶ

τοὺς ὑποκειμένους ὅρους ἢ τοὺς αὐτοὺς εἶναι ἢ τὸν μὲν ὅλον

τὸν δὲ μέρος. δῆλον δὲ καὶ ὅτι ἐν τοῖς παραλογισμοῖς οὐδὲν

κωλύει γίνεσθαι τῆς ὑποθέσεως ἀντίφασιν, οἷον εἰ ἔστι περιττόν,

15 μὴ εἶναι περιττόν. ἐκ γὰρ τῶν ἀντικειμένων προτάσεων

ἐναντίος ἦν ὁ συλλογισμός· ἐὰν οὖν λάβῃ τοιαύτας, ἔσται τῆς

ὑποθέσεως ἀντίφασις, δεῖ δὲ κατανοεῖν ὅτι οὕτω μὲν οὐκ ἔστιν

ἐναντία συμπεράνασθαι ἐξ ἑνὸς συλλογισμοῦ ὥστ' εἶναι τὸ

συμπέρασμα τὸ μὴ ὂν ἀγαθὸν ἀγαθὸν ἢ ἄλλο τι τοιοῦτον,

20 ἐὰν μὴ εὐθὺς ἡ πρότασις τοιαύτη ληφθῇ (οἷον πᾶν ζῷον λευκὸν

εἶναι καὶ μὴ λευκόν, τὸν δ' ἄνθρωπον ζῷον), ἀλλ' ἢ προςλαβεῖν

δεῖ τὴν ἀντίφασιν (οἷον ὅτι πᾶσα ἐπιστήμη ὑπόληψις

[καὶ οὐχ ὑπόληψις], εἶτα λαβεῖν ὅτι ἡ ἰατρικὴ ἐπιστήμη

μέν ἐστιν, οὐδεμία δ' ὑπόληψις, ὥσπερ οἱ ἔλεγχοι γίνονται),

25 ἢ ἐκ δύο συλλογισμῶν. ὥστε δ' εἶναι ἐναντία κατ' ἀλήθειαν

τὰ εἰλημμένα, οὐκ ἔστιν ἄλλον τρόπον ἢ τοῦτον, καθάπερ

εἴρηται πρότερον.

1A may belong to all B and to no C, or to all C and to no B, or to all of the one, not to all of the other; here too the relation between the terms may be reversed. Similarly in the third figure. So it is clear in how many ways and 5in what figures a syllogism can be made by means of premisses which are opposed.
It is clear too that from false premisses it is possible to draw a true conclusion, as has been said before, but it is not possible if the premisses are opposed. For the syllogism is always contrary to 10the fact, e.g. if a thing is good, it is proved that it is not good, if an animal, that it is not an animal because the syllogism springs out of a contradiction and the terms presupposed are either identical or related as whole and part. It is evident also that in fallacious reasonings nothing prevents a contradiction to the hypothesis from resulting, e.g. if something is odd, 15it is not odd. For the syllogism owed its contrariety to its contradictory premisses; if we assume such premisses we shall get a result that contradicts our hypothesis. But we must recognize that contraries cannot be inferred from a single syllogism in such a way that we conclude that what is not good is good, or anything of that sort 20unless a self-contradictory premiss is at once assumed, e.g. 'every animal is white and not white', and we proceed 'man is an animal'. Either we must introduce the contradiction by an additional assumption, assuming, e.g., that every science is supposition, and then assuming 'Medicine is a science, but none of it is supposition' (which is the mode in which refutations are made), 25or we must argue from two syllogisms. In no other way than this, as was said before, is it possible that the premisses should be really contrary.

Book 2,Chapter 16 (64b28–65a37)

Τὸ δ' ἐν ἀρχῇ αἰτεῖσθαι καὶ λαμβάνειν ἐστὶ μέν, ὡς

ἐν γένει λαβεῖν, ἐν τῷ μὴ ἀποδεικνύναι τὸ προκείμενον, τοῦτο

30 δὲ συμβαίνει πολλαχῶς· καὶ γὰρ εἰ ὅλως μὴ συλλογίζεται,

καὶ εἰ δι' ἀγνωστοτέρων ἢ ὁμοίως ἀγνώστων, καὶ

εἰ διὰ τῶν ὑστέρων τὸ πρότερον· ἡ γὰρ ἀπόδειξις ἐκ πιστοτέρων

τε καὶ προτέρων ἐστίν. τούτων μὲν οὖν οὐδέν ἐστι τὸ αἰτεῖσθαι

τὸ ἐξ ἀρχῆς· ἀλλ' ἐπεὶ τὰ μὲν δι' αὑτῶν πέφυκε

35 γνωρίζεσθαι τὰ δὲ δι' ἄλλων (αἱ μὲν γὰρ ἀρχαὶ δι' αὑτῶν,

τὰ δ' ὑπὸ τὰς ἀρχὰς δι' ἄλλων), ὅταν μὴ τὸ δι'

αὑτοῦ γνωστὸν δι' αὑτοῦ τις ἐπιχειρῇ δεικνύναι, τότ' αἰτεῖται

τὸ ἐξ ἀρχῆς. τοῦτο δ' ἔστι μὲν οὕτω ποιεῖν ὥστ' εὐθὺς ἀξιῶσαι

τὸ προκείμενον, ἐνδέχεται δὲ καὶ μεταβάντας ἐπ'

40 ἄλλα ἄττα τῶν πεφυκότων δι' ἐκείνου δείκνυσθαι διὰ τούτων

28To beg and assume the original question is a species of failure to demonstrate the problem proposed; 30but this happens in many ways. A man may not reason syllogistically at all, or he may argue from premisses which are less known or equally unknown, or he may establish the antecedent by means of its consequents; for demonstration proceeds from what is more certain and is prior. Now begging the question is none of these: but since we get to know some things naturally through themselves, 35and other things by means of something else (the first principles through themselves, what is subordinate to them through something else), whenever a man tries to prove what is not self-evident by means of itself, then he begs the original question. This may be done by assuming what is in question at once; it is also possible 40to make a transition to other things which would naturally be proved through the thesis proposed, and demonstrate it through them, e.g.

65a

1 ἀποδεικνύναι τὸ ἐξ ἀρχῆς, οἷον εἰ τὸ Α δεικνύοιτο διὰ τοῦ

Β, τὸ δὲ Β διὰ τοῦ Γ, τὸ δὲ Γ πεφυκὸς εἴη δείκνυσθαι

διὰ τοῦ Α· συμβαίνει γὰρ αὐτὸ δι' αὑτοῦ τὸ Α δεικνύναι

τοὺς οὕτω συλλογιζομένους. ὅπερ ποιοῦσιν οἱ τὰς παραλλήλους

5 οἰόμενοι γράφειν· λανθάνουσι γὰρ αὐτοὶ ἑαυτοὺς τοιαῦτα

λαμβάνοντες ἃ οὐχ οἷόν τε ἀποδεῖξαι μὴ οὐσῶν τῶν

παραλλήλων. ὥστε συμβαίνει τοῖς οὕτω συλλογιζομένοις ἕκαστον

εἶναι λέγειν, εἰ ἔστιν ἕκαστον· οὕτω δ' ἅπαν ἔσται δι' αὑτοῦ

γνωστόν· ὅπερ ἀδύνατον.

10 Εἰ οὖν τις ἀδήλου ὄντος ὅτι τὸ Α ὑπάρχει τῷ Γ,

ὁμοίως δὲ καὶ ὅτι τῷ Β, αἰτοῖτο τῷ Β ὑπάρχειν τὸ Α,

οὔπω δῆλον εἰ τὸ ἐν ἀρχῇ αἰτεῖται, ἀλλ' ὅτι οὐκ ἀποδείκνυσι,

δῆλον· οὐ γὰρ ἀρχὴ ἀποδείξεως τὸ ὁμοίως ἄδηλον.

εἰ μέντοι τὸ Β πρὸς τὸ Γ οὕτως ἔχει ὥστε ταὐτὸν εἶναι, ἢ

15 δῆλον ὅτι ἀντιστρέφουσιν, ἢ ἐνυπάρχει θάτερον θατέρῳ, τὸ ἐν

ἀρχῇ αἰτεῖται. καὶ γὰρ ἂν ὅτι τῷ Β τὸ Α ὑπάρχει δι'

ἐκείνων δεικνύοι, εἰ ἀντιστρέφοι (νῦν δὲ τοῦτο κωλύει, ἀλλ'

οὐχ ὁ τρόπος). εἰ δὲ τοῦτο ποιοῖ, τὸ εἰρημένον ἂν ποιοῖ καὶ

ἀντιστρέφοι διὰ τριῶν. ὡσαύτως δὲ κἂν εἰ τὸ Β τῷ Γ

20 λαμβάνοι ὑπάρχειν, ὁμοίως ἄδηλον ὂν καὶ εἰ τὸ Α, οὔπω

τὸ ἐξ ἀρχῆς, ἀλλ' οὐκ ἀποδείκνυσιν. ἐὰν δὲ ταὐτὸν

ᾖ τὸ Α καὶ Β ἢ τῷ ἀντιστρέφειν ἢ τῷ ἕπεσθαι τῷ Β

τὸ Α, τὸ ἐξ ἀρχῆς αἰτεῖται διὰ τὴν αὐτὴν αἰτίαν· τὸ γὰρ

ἐξ ἀρχῆς τί δύναται, εἴρηται ἡμῖν, ὅτι τὸ δι' αὑτοῦ δεικνύναι

25 τὸ μὴ δι' αὑτοῦ δῆλον.

Εἰ οὖν ἐστι τὸ ἐν ἀρχῇ αἰτεῖσθαι τὸ δι' αὑτοῦ δεικνύναι

τὸ μὴ δι' αὑτοῦ δῆλον, τοῦτο δ' ἐστὶ τὸ μὴ δεικνύναι, ὅταν

ὁμοίως ἀδήλων ὄντων τοῦ δεικνυμένου καὶ δι' οὗ δείκνυσιν ἢ

τῷ ταὐτὰ τῷ αὐτῷ ἢ τῷ ταὐτὸν τοῖς αὐτοῖς ὑπάρχειν, ἐν

30 μὲν τῷ μέσῳ σχήματι καὶ τρίτῳ ἀμφοτέρως ἂν ἐνδέχοιτο

τὸ ἐν ἀρχῇ αἰτεῖσθαι, ἐν δὲ κατηγορικῷ συλλογισμῷ ἔν

τε τῷ τρίτῳ καὶ τῷ πρώτῳ. ὅταν δ' ἀποφατικῶς, ὅταν τὰ

αὐτὰ ἀπὸ τοῦ αὐτοῦ· καὶ οὐχ ὁμοίως ἀμφότεραι αἱ προτάσεις

(ὡσαύτως δὲ καὶ ἐν τῷ μέσῳ), διὰ τὸ μὴ ἀντιστρέφειν

35 τοὺς ὅρους κατὰ τοὺς ἀποφατικοὺς συλλογισμούς. ἔστι δὲ

τὸ ἐν ἀρχῇ αἰτεῖσθαι ἐν μὲν ταῖς ἀποδείξεσι τὰ κατ' ἀλήθειαν

οὕτως ἔχοντα, ἐν δὲ τοῖς διαλεκτικοῖς τὰ κατὰ δόξαν.

1if A should be proved through B, and B through C, though it was natural that C should be proved through A: for it turns out that those who reason thus are proving A by means of itself. This is what those persons do who suppose that they are constructing parallel straight lines: 5for they fail to see that they are assuming facts which it is impossible to demonstrate unless the parallels exist. So it turns out that those who reason thus merely say a particular thing is, if it is: in this way everything will be self-evident. But that is impossible.
10If then it is uncertain whether A belongs to C, and also whether A belongs to B, and if one should assume that A does belong to B, it is not yet clear whether he begs the original question, but it is evident that he is not demonstrating: for what is as uncertain as the question to be answered cannot be a principle of a demonstration. If however B is so related to C that they are identical, 15or if they are plainly convertible, or the one belongs to the other, the original question is begged. For one might equally well prove that A belongs to B through those terms if they are convertible. But if they are not convertible, it is the fact that they are not that prevents such a demonstration, not the method of demonstrating. But if one were to make the conversion, then he would be doing what we have described and effecting a reciprocal proof with three propositions.
Similarly if he should assume that B belongs to C, 20this being as uncertain as the question whether A belongs to C, the question is not yet begged, but no demonstration is made. If however A and B are identical either because they are convertible or because A follows B, then the question is begged for the same reason as before. For we have explained the meaning of begging the question, viz. 25proving that which is not self-evident by means of itself.
If then begging the question is proving what is not self-evident by means of itself, in other words failing to prove when the failure is due to the thesis to be proved and the premiss through which it is proved being equally uncertain, either because predicates which are identical belong to the same subject, or because the same predicate belongs to subjects which are identical, 30the question may be begged in the middle and third figures in both ways, though, if the syllogism is affirmative, only in the third and first figures. If the syllogism is negative, the question is begged when identical predicates are denied of the same subject; and both premisses do not beg the question indifferently (in a similar way the question may be begged in the middle figure), 35because the terms in negative syllogisms are not convertible. In scientific demonstrations the question is begged when the terms are really related in the manner described, in dialectical arguments when they are according to common opinion so related.

Book 2,Chapter 17 (65a38–66a15)

Τὸ δὲ μὴ παρὰ τοῦτο συμβαίνειν τὸ ψεῦδος, ὃ πολλάκις

ἐν τοῖς λόγοις εἰώθαμεν λέγειν, πρῶτον μέν ἐστιν ἐν

40 τοῖς εἰς τὸ ἀδύνατον συλλογισμοῖς, ὅταν πρὸς ἀντίφασιν ᾖ

38The objection that 'this is not the reason why the result is false', which we frequently make in argument, is made primarily 40in the case of a reductio ad impossibile, to rebut the proposition which was being proved by the reduction.

65b

1 τούτου ὃ ἐδείκνυτο τῇ εἰς τὸ ἀδύνατον. οὔτε γὰρ μὴ ἀντιφήσας

ἐρεῖ τὸ οὐ παρὰ τοῦτο, ἀλλ' ὅτι ψεῦδός τι ἐτέθη

τῶν πρότερον, οὔτ' ἐν τῇ δεικνυούσῃ· οὐ γὰρ τίθησι ὃ ἀντίφησιν.

ἔτι δ' ὅταν ἀναιρεθῇ τι δεικτικῶς διὰ τῶν Α Β Γ, οὐκ

5 ἔστιν εἰπεῖν ὡς οὐ παρὰ τὸ κείμενον γεγένηται ὁ συλλογισμός.

τὸ γὰρ μὴ παρὰ τοῦτο γίνεσθαι τότε λέγομεν, ὅταν

ἀναιρεθέντος τούτου μηδὲν ἧττον περαίνηται ὁ συλλογισμός,

ὅπερ οὐκ ἔστιν ἐν τοῖς δεικτικοῖς· ἀναιρεθείσης γὰρ τῆς θέσεως

οὐδ' ὁ πρὸς ταύτην ἔσται συλλογισμός. φανερὸν οὖν ὅτι ἐν τοῖς

10 εἰς τὸ ἀδύνατον λέγεται τὸ μὴ παρὰ τοῦτο, καὶ ὅταν οὕτως

ἔχῃ πρὸς τὸ ἀδύνατον ἡ ἐξ ἀρχῆς ὑπόθεσις ὥστε καὶ οὔσης

καὶ μὴ οὔσης ταύτης οὐδὲν ἧττον συμβαίνειν τὸ ἀδύνατον.

Ὁ μὲν οὖν φανερώτατος τρόπος ἐστὶ τοῦ μὴ παρὰ τὴν

θέσιν εἶναι τὸ ψεῦδος, ὅταν ἀπὸ τῆς ὑποθέσεως ἀσύναπτος

15 ᾖ ἀπὸ τῶν μέσων πρὸς τὸ ἀδύνατον ὁ συλλογισμός, ὅπερ

εἴρηται καὶ ἐν τοῖς Τοπικοῖς. τὸ γὰρ τὸ ἀναίτιον ὡς αἴτιον τιθέναι

τοῦτό ἐστιν, οἷον εἰ βουλόμενος δεῖξαι ὅτι ἀσύμμετρος

ἡ διάμετρος, ἐπιχειροίη τὸν Ζήνωνος λόγον, ὡς

οὐκ ἔστι κινεῖσθαι, καὶ εἰς τοῦτο ἀπάγοι τὸ ἀδύνατον· οὐδαμῶς

20 γὰρ οὐδαμῇ συνεχές ἐστι τὸ ψεῦδος τῇ φάσει τῇ ἐξ

ἀρχῆς. ἄλλος δὲ τρόπος, εἰ συνεχὲς μὲν εἴη τὸ ἀδύνατον

τῇ ὑποθέσει, μὴ μέντοι δι' ἐκείνην συμβαίνοι. τοῦτο γὰρ

ἐγχωρεῖ γενέσθαι καὶ ἐπὶ τὸ ἄνω καὶ ἐπὶ τὸ κάτω λαμβάνοντι

τὸ συνεχές, οἷον εἰ τὸ Α τῷ Β κεῖται ὑπάρχον,

25 τὸ δὲ Β τῷ Γ, τὸ δὲ Γ τῷ Δ, τοῦτο δ' εἴη ψεῦδος,

τὸ τὸ Β τῷ Δ ὑπάρχειν. εἰ γὰρ ἀφαιρεθέντος τοῦ Α μηδὲν

ἧττον ὑπάρχοι τὸ Β τῷ Γ καὶ τὸ Γ τῷ Δ, οὐκ ἂν εἴη τὸ

ψεῦδος διὰ τὴν ἐξ ἀρχῆς ὑπόθεσιν. ἢ πάλιν εἴ τις ἐπὶ τὸ

ἄνω λαμβάνοι τὸ συνεχές, οἷον εἰ τὸ μὲν Α τῷ Β, τῷ δὲ

30 Α τὸ Ε καὶ τῷ Ε τὸ Ζ, ψεῦδος δ' εἴη τὸ ὑπάρχειν τῷ

Α τὸ Ζ· καὶ γὰρ οὕτως οὐδὲν ἂν ἧττον εἴη τὸ ἀδύνατον

ἀναιρεθείσης τῆς ἐξ ἀρχῆς ὑποθέσεως. ἀλλὰ δεῖ πρὸς τοὺς

ἐξ ἀρχῆς ὅρους συνάπτειν τὸ ἀδύνατον· οὕτω γὰρ ἔσται διὰ

τὴν ὑπόθεσιν, οἷον ἐπὶ μὲν τὸ κάτω λαμβάνοντι τὸ συνεχὲς

35 πρὸς τὸν κατηγορούμενον τῶν ὅρων (εἰ γὰρ ἀδύνατον τὸ Α

τῷ Δ ὑπάρχειν, ἀφαιρεθέντος τοῦ Α οὐκέτι ἔσται τὸ ψεῦδος)·

ἐπὶ δὲ τὸ ἄνω, καθ' οὗ κατηγορεῖται (εἰ γὰρ τῷ Β μὴ ἐγχωρεῖ

τὸ Ζ ὑπάρχειν, ἀφαιρεθέντος τοῦ Β οὐκέτι ἔσται τὸ

ἀδύνατον). ὁμοίως δὲ καὶ στερητικῶν τῶν συλλογισμῶν

40 ὄντων.

1For unless a man has contradicted this proposition he will not say, 'False cause', but urge that something false has been assumed in the earlier parts of the argument; nor will he use the formula in the case of an ostensive proof; for here what one denies is not assumed as a premiss. Further when anything is refuted ostensively by the terms ABC, 5it cannot be objected that the syllogism does not depend on the assumption laid down. For we use the expression 'false cause', when the syllogism is concluded in spite of the refutation of this position; but that is not possible in ostensive proofs: since if an assumption is refuted, a syllogism can no longer be drawn in reference to it. It is clear then that the expression 'false cause' can only be used 10in the case of a reductio ad impossibile, and when the original hypothesis is so related to the impossible conclusion, that the conclusion results indifferently whether the hypothesis is made or not. The most obvious case of the irrelevance of an assumption to a conclusion which is false is when a syllogism drawn 15from middle terms to an impossible conclusion is independent of the hypothesis, as we have explained in the Topics. For to put that which is not the cause as the cause, is just this: e.g. if a man, wishing to prove that the diagonal of the square is incommensurate with the side, should try to prove Zeno's theorem that motion is impossible, and so establish a reductio ad impossibile: 20for Zeno's false theorem has no connexion at all with the original assumption. Another case is where the impossible conclusion is connected with the hypothesis, but does not result from it. This may happen whether one traces the connexion upwards or downwards, e.g. if it is laid down that A belongs to B, 25B to C, and C to D, and it should be false that B belongs to D: for if we eliminated A and assumed all the same that B belongs to C and C to D, the false conclusion would not depend on the original hypothesis. Or again trace the connexion upwards; e.g. suppose that A belongs to B, 30E to A and F to E, it being false that F belongs to A. In this way too the impossible conclusion would result, though the original hypothesis were eliminated. But the impossible conclusion ought to be connected with the original terms: in this way it will depend on the hypothesis, e.g. when one traces the connexion downwards, the impossible conclusion must be connected 35with that term which is predicate in the hypothesis: for if it is impossible that A should belong to D, the false conclusion will no longer result after A has been eliminated. If one traces the connexion upwards, the impossible conclusion must be connected with that term which is subject in the hypothesis: for if it is impossible that F should belong to B, the impossible conclusion will disappear if B is eliminated. 40Similarly when the syllogisms are negative.

66a

1 Φανερὸν οὖν ὅτι τοῦ ἀδυνάτου μὴ πρὸς τοὺς ἐξ ἀρχῆς

ὅρους ὄντος οὐ παρὰ τὴν θέσιν συμβαίνει τὸ ψεῦδος. ἢ οὐδ'

οὕτως ἀεὶ διὰ τὴν ὑπόθεσιν ἔσται τὸ ψεῦδος; καὶ γὰρ εἰ μὴ

τῷ Β ἀλλὰ τῷ Κ ἐτέθη τὸ Α ὑπάρχειν, τὸ δὲ Κ τῷ Γ

5 καὶ τοῦτο τῷ Δ, καὶ οὕτω μένει τὸ ἀδύνατον (ὁμοίως δὲ καὶ

ἐπὶ τὸ ἄνω λαμβάνοντι τοὺς ὅρους), ὥστ' ἐπεὶ καὶ ὄντος καὶ

μὴ ὄντος τούτου συμβαίνει τὸ ἀδύνατον, οὐκ ἂν εἴη παρὰ

τὴν θέσιν. ἢ τὸ μὴ ὄντος τούτου μηδὲν ἧττον γίνεσθαι τὸ ψεῦδος

οὐχ οὕτω ληπτέον ὥστ' ἄλλου τιθεμένου συμβαίνειν τὸ

10 ἀδύνατον, ἀλλ' ὅταν ἀφαιρεθέντος τούτου διὰ τῶν λοιπῶν

προτάσεων ταὐτὸ περαίνηται ἀδύνατον, ἐπεὶ ταὐτό γε ψεῦδος

συμβαίνειν διὰ πλειόνων ὑποθέσεων οὐδὲν ἴσως ἄτοπον,

οἷον τὰς παραλλήλους συμπίπτειν καὶ εἰ μείζων ἐστὶν ἡ

ἐντὸς τῆς ἐκτὸς καὶ εἰ τὸ τρίγωνον ἔχει πλείους ὀρθὰς

15 δυεῖν;

1It is clear then that when the impossibility is not related to the original terms, the false conclusion does not result on account of the assumption. Or perhaps even so it may sometimes be independent. For if it were laid down that A belongs not to B but to K, 5and that K belongs to C and C to D, the impossible conclusion would still stand. Similarly if one takes the terms in an ascending series. Consequently since the impossibility results whether the first assumption is suppressed or not, it would appear to be independent of that assumption. Or perhaps we ought not to understand the statement that the false conclusion results independently of the assumption, in the sense that if something else were supposed the impossibility would result; 10but rather we mean that when the first assumption is eliminated, the same impossibility results through the remaining premisses; since it is not perhaps absurd that the same false result should follow from several hypotheses, e.g. that parallels meet, both on the assumption that the interior angle is greater than the exterior and on the assumption that a triangle contains more 15than two right angles.

Book 2,Chapter 18 (66a16–24)

Ὁ δὲ ψευδὴς λόγος γίνεται παρὰ τὸ πρῶτον ψεῦδος.

ἢ γὰρ ἐκ τῶν δύο προτάσεων ἢ ἐκ πλειόνων πᾶς ἐστι συλλογισμός.

εἰ μὲν οὖν ἐκ τῶν δύο, τούτων ἀνάγκη τὴν ἑτέραν

ἢ καὶ ἀμφοτέρας εἶναι ψευδεῖς· ἐξ ἀληθῶν γὰρ οὐκ ἦν ψευδὴς

20 συλλογισμός. εἰ δ' ἐκ πλειόνων, οἷον τὸ μὲν Γ διὰ τῶν

Α Β, ταῦτα δὲ διὰ τῶν Δ Ε Ζ Η, τούτων τι ἔσται τῶν

ἐπάνω ψεῦδος, καὶ παρὰ τοῦτο ὁ λόγος· τὸ γὰρ Α καὶ Β

δι' ἐκείνων περαίνονται. ὥστε παρ' ἐκείνων τι συμβαίνει τὸ

συμπέρασμα καὶ τὸ ψεῦδος.

16A false argument depends on the first false statement in it. Every syllogism is made out of two or more premisses. If then the false conclusion is drawn from two premisses, one or both of them must be false: for (as we proved) a false syllogism cannot be drawn from two premisses. 20But if the premisses are more than two, e.g. if C is established through A and B, and these through D, E, F, and G, one of these higher propositions must be false, and on this the argument depends: for A and B are inferred by means of D, E, F, and G. Therefore the conclusion and the error results from one of them.

Book 2,Chapter 19 (66a25–66b3)

25 Πρὸς δὲ τὸ μὴ κατασυλλογίζεσθαι παρατηρητέον,

ὅταν ἄνευ τῶν συμπερασμάτων ἐρωτᾷ τὸν λόγον, ὅπως μὴ

δοθῇ δὶς ταὐτὸν ἐν ταῖς προτάσεσιν, ἐπειδήπερ ἴσμεν ὅτι

ἄνευ μέσου συλλογισμὸς οὐ γίνεται, μέσον δ' ἐστὶ τὸ πλεονάκις

λεγόμενον. ὡς δὲ δεῖ πρὸς ἕκαστον συμπέρασμα τηρεῖν

30 τὸ μέσον, φανερὸν ἐκ τοῦ εἰδέναι ποῖον ἐν ἑκάστῳ σχήματι

δείκνυται. τοῦτο δ' ἡμᾶς οὐ λήσεται διὰ τὸ εἰδέναι πῶς

ὑπέχομεν τὸν λόγον.

Χρὴ δ' ὅπερ φυλάττεσθαι παραγγέλλομεν ἀποκρινομένους,

αὐτοὺς ἐπιχειροῦντας πειρᾶσθαι λανθάνειν. τοῦτο δ'

35 ἔσται πρῶτον, ἐὰν τὰ συμπεράσματα μὴ προσυλλογίζωνται

ἀλλ' εἰλημμένων τῶν ἀναγκαίων ἄδηλα ᾖ, ἔτι δὲ ἂν

μὴ τὰ σύνεγγυς ἐρωτᾷ, ἀλλ' ὅτι μάλιστα ἄμεσα. οἷον

ἔστω δέον συμπεραίνεσθαι τὸ Α κατὰ τοῦ Ζ· μέσα Β Γ Δ Ε.

δεῖ οὖν ἐρωτᾶν εἰ τὸ Α τῷ Β, καὶ πάλιν μὴ εἰ τὸ Β τῷ

40 Γ, ἀλλ' εἰ τὸ Δ τῷ Ε, κἄπειτα εἰ τὸ Β τῷ Γ, καὶ οὕτω

25In order to avoid having a syllogism drawn against us we must take care, whenever an opponent asks us to admit the reason without the conclusions, not to grant him the same term twice over in his premisses, since we know that a syllogism cannot be drawn without a middle term, and that term which is stated more than once is the middle. How we ought to watch the middle in reference to each conclusion, 30is evident from our knowing what kind of thesis is proved in each figure. This will not escape us since we know how we are maintaining the argument.
That which we urge men to beware of in their admissions, they ought in attack to try to conceal. This 35will be possible first, if, instead of drawing the conclusions of preliminary syllogisms, they take the necessary premisses and leave the conclusions in the dark; secondly if instead of inviting assent to propositions which are closely connected they take as far as possible those that are not connected by middle terms. For example suppose that A is to be inferred to be true of F, B, C, D, and E being middle terms. One ought then to ask whether A belongs to B, and next 40whether D belongs to E, instead of asking whether B belongs to C; after that he may ask whether B belongs to C, and so on.

66b

1 τὰ λοιπά. κἂν δι' ἑνὸς μέσου γίνηται ὁ συλλογισμός, ἀπὸ

τοῦ μέσου ἄρχεσθαι· μάλιστα γὰρ ἂν οὕτω λανθάνοι τὸν

ἀποκρινόμενον.

1If the syllogism is drawn through one middle term, he ought to begin with that: in this way he will most likely deceive his opponent.

Book 2,Chapter 20 (66b4–17)

Ἐπεὶ δ' ἔχομεν πότε καὶ πῶς ἐχόντων τῶν ὅρων γίνεται

5 συλλογισμός, φανερὸν καὶ πότ' ἔσται καὶ πότ' οὐκ

ἔσται ἔλεγχος. πάντων μὲν γὰρ συγχωρουμένων, ἢ ἐναλλὰξ

τιθεμένων τῶν ἀποκρίσεων, οἷον τῆς μὲν ἀποφατικῆς τῆς δὲ

καταφατικῆς, ἐγχωρεῖ γίνεσθαι ἔλεγχον. ἦν γὰρ συλλογισμὸς

καὶ οὕτω καὶ ἐκείνως ἐχόντων τῶν ὅρων, ὥστ' εἰ τὸ

10 κείμενον ἐναντίον τῷ συμπεράσματι, ἀνάγκη γίνεσθαι ἔλεγχον·

ὁ γὰρ ἔλεγχος ἀντιφάσεως συλλογισμός. εἰ δὲ μηδὲν

συγχωροῖτο, ἀδύνατον γενέσθαι ἔλεγχον· οὐ γὰρ ἦν

συλλογισμὸς πάντων τῶν ὅρων στερητικῶν ὄντων, ὥστ' οὐδ'

ἔλεγχος· εἰ μὲν γὰρ ἔλεγχος, ἀνάγκη συλλογισμὸν εἶναι,

15 συλλογισμοῦ δ' ὄντος οὐκ ἀνάγκη ἔλεγχον. ὡσαύτως δὲ καὶ

εἰ μηδὲν τεθείη κατὰ τὴν ἀπόκρισιν ἐν ὅλῳ· ὁ γὰρ αὐτὸς

ἔσται διορισμὸς ἐλέγχου καὶ συλλογισμοῦ.

4Since we know when a syllogism can be formed and how its terms must be related, 5it is clear when refutation will be possible and when impossible. A refutation is possible whether everything is conceded, or the answers alternate (one, I mean, being affirmative, the other negative). For as has been shown a syllogism is possible whether the terms are related in affirmative propositions or one proposition is affirmative, the other negative: consequently, if 10what is laid down is contrary to the conclusion, a refutation must take place: for a refutation is a syllogism which establishes the contradictory. But if nothing is conceded, a refutation is impossible: for no syllogism is possible (as we saw) when all the terms are negative: therefore no refutation is possible. For if a refutation were possible, a syllogism must be possible; 15although if a syllogism is possible it does not follow that a refutation is possible. Similarly refutation is not possible if nothing is conceded universally: since the fields of refutation and syllogism are defined in the same way.

Book 2,Chapter 21 (66b18–67b26)

Συμβαίνει δ' ἐνίοτε, καθάπερ ἐν τῇ θέσει τῶν ὅρων

ἀπατώμεθα, καὶ κατὰ τὴν ὑπόληψιν γίνεσθαι τὴν ἀπάτην,

20 οἷον εἰ ἐνδέχεται τὸ αὐτὸ πλείοσι πρώτοις ὑπάρχειν, καὶ

τὸ μὲν λεληθέναι τινὰ καὶ οἴεσθαι μηδενὶ ὑπάρχειν, τὸ δὲ

εἰδέναι. ἔστω τὸ Α τῷ Β καὶ τῷ Γ καθ' αὑτὰ ὑπάρχον,

καὶ ταῦτα παντὶ τῷ Δ ὡσαύτως. εἰ δὴ τῷ μὲν Β τὸ

Α παντὶ οἴεται ὑπάρχειν, καὶ τοῦτο τῷ Δ, τῷ δὲ Γ τὸ Α

25 μηδενί, καὶ τοῦτο τῷ Δ παντί, τοῦ αὐτοῦ κατὰ ταὐτὸν ἕξει

ἐπιστήμην καὶ ἄγνοιαν. πάλιν εἴ τις ἀπατηθείη περὶ τὰ ἐκ

τῆς αὐτῆς συστοιχίας, οἷον εἰ τὸ Α ὑπάρχει τῷ Β, τοῦτο δὲ

τῷ Γ καὶ τὸ Γ τῷ Δ, ὑπολαμβάνοι δὲ τὸ Α παντὶ τῷ Β

ὑπάρχειν καὶ πάλιν μηδενὶ τῷ Γ· ἅμα γὰρ εἴσεταί τε καὶ

30 οὐχ ὑπολήψεται ὑπάρχειν. ἆρ' οὖν οὐδὲν ἄλλο ἀξιοῖ ἐκ τούτων

ἢ ὃ ἐπίσταται, τοῦτο μὴ ὑπολαμβάνειν; ἐπίσταται γάρ

πως ὅτι τὸ Α τῷ Γ ὑπάρχει διὰ τοῦ Β, ὡς τῇ καθόλου τὸ

κατὰ μέρος, ὥστε ὅ πως ἐπίσταται, τοῦτο ὅλως ἀξιοῖ μὴ

ὑπολαμβάνειν· ὅπερ ἀδύνατον. Ἐπὶ δὲ τοῦ πρότερον λεχθέντος,

35 εἰ μὴ ἐκ τῆς αὐτῆς συστοιχίας τὸ μέσον, καθ' ἑκάτερον

μὲν τῶν μέσων ἀμφοτέρας τὰς προτάσεις οὐκ ἐγχωρεῖ

ὑπολαμβάνειν, οἷον τὸ Α τῷ μὲν Β παντί, τῷ δὲ Γ μηδενί,

ταῦτα δ' ἀμφότερα παντὶ τῷ Δ. συμβαίνει γὰρ ἢ

ἁπλῶς ἢ ἐπί τι ἐναντίαν λαμβάνεσθαι τὴν πρώτην πρότασιν.

40 εἰ γὰρ ᾧ τὸ Β ὑπάρχει, παντὶ τὸ Α ὑπολαμβάνει

18It sometimes happens that just as we are deceived in the arrangement of the terms, so error may arise in our thought about them, 20e.g. if it is possible that the same predicate should belong to more than one subject immediately, but although knowing the one, a man may forget the other and think the opposite true. Suppose that A belongs to B and to C in virtue of their nature, and that B and C belong to all D in the same way. If then a man thinks that A belongs to all B, and B to D, 25but A to no C, and C to all D, he will both know and not know the same thing in respect of the same thing. Again if a man were to make a mistake about the members of a single series; e.g. suppose A belongs to B, B to C, and C to D, but some one thinks that A belongs to all B, but to no C: he will both know that A belongs to D, 30and think that it does not. Does he then maintain after this simply that what he knows, he does not think? For he knows in a way that A belongs to C through B, since the part is included in the whole; so that what he knows in a way, this he maintains he does not think at all: but that is impossible.
In the former case, 35where the middle term does not belong to the same series, it is not possible to think both the premisses with reference to each of the two middle terms: e.g. that A belongs to all B, but to no C, and both B and C belong to all D. For it turns out that the first premiss of the one syllogism is either wholly or partially contrary to the first premiss of the other. 40For if he thinks that A belongs to everything to which B belongs, and he knows that B belongs to D, then he knows that A belongs to D.

67a

1 ὑπάρχειν, τὸ δὲ Β τῷ Δ οἶδε, καὶ ὅτι τῷ Δ τὸ Α οἶδεν.

ὥστ' εἰ πάλιν, ᾧ τὸ Γ, μηδενὶ οἴεται τὸ Α ὑπάρχειν, ᾧ τὸ

Β τινὶ ὑπάρχει, τούτῳ οὐκ οἴεται τὸ Α ὑπάρχειν. τὸ δὲ

παντὶ οἰόμενον ᾧ τὸ Β, πάλιν τινὶ μὴ οἴεσθαι ᾧ τὸ Β, ἢ

5 ἁπλῶς ἢ ἐπί τι ἐναντίον ἐστίν. Οὕτω μὲν οὖν οὐκ ἐνδέχεται

ὑπολαβεῖν, καθ' ἑκάτερον δὲ τὴν μίαν ἢ κατὰ θάτερον ἀμφοτέρας

οὐδὲν κωλύει, οἷον τὸ Α παντὶ τῷ Β καὶ τὸ Β τῷ

Δ, καὶ πάλιν τὸ Α μηδενὶ τῷ Γ. ὁμοία γὰρ ἡ τοιαύτη

ἀπάτη καὶ ὡς ἀπατώμεθα περὶ τὰς ἐν μέρει, οἷον εἰ ᾧ τὸ Β,

10 παντὶ τὸ Α ὑπάρχει, τὸ δὲ Β τῷ Γ παντί, τὸ Α παντὶ

τῷ Γ ὑπάρξει. εἰ οὖν τις οἶδεν ὅτι τὸ Α, ᾧ τὸ Β, ὑπάρχει

παντί, οἶδε καὶ ὅτι τῷ Γ. ἀλλ' οὐδὲν κωλύει ἀγνοεῖν

τὸ Γ ὅτι ἔστιν, οἷον εἰ τὸ μὲν Α δύο ὀρθαί, τὸ δ' ἐφ' ᾧ Β

τρίγωνον, τὸ δ' ἐφ' ᾧ Γ αἰσθητὸν τρίγωνον. ὑπολάβοι γὰρ

15 ἄν τις μὴ εἶναι τὸ Γ, εἰδὼς ὅτι πᾶν τρίγωνον ἔχει δύο ὀρθάς,

ὥσθ' ἅμα εἴσεται καὶ ἀγνοήσει ταὐτόν. τὸ γὰρ εἰδέναι

πᾶν τρίγωνον ὅτι δύο ὀρθαῖς οὐχ ἁπλοῦν ἐστιν, ἀλλὰ

τὸ μὲν τῷ τὴν καθόλου ἔχειν ἐπιστήμην, τὸ δὲ τὴν καθ'

ἕκαστον. οὕτω μὲν οὖν ὡς τῇ καθόλου οἶδε τὸ Γ ὅτι δύο ὀρθαί,

20 ὡς δὲ τῇ καθ' ἕκαστον οὐκ οἶδεν, ὥστ' οὐχ ἕξει τὰς

ἐναντίας. ὁμοίως δὲ καὶ ὁ ἐν τῷ Μένωνι λόγος, ὅτι ἡ μάθησις

ἀνάμνησις. οὐδαμοῦ γὰρ συμβαίνει προεπίστασθαι τὸ

καθ' ἕκαστον, ἀλλ' ἅμα τῇ ἐπαγωγῇ λαμβάνειν τὴν τῶν

κατὰ μέρος ἐπιστήμην ὥσπερ ἀναγνωρίζοντας. ἔνια γὰρ εὐθὺς

25 ἴσμεν, οἷον ὅτι δύο ὀρθαῖς, ἐὰν ἴδωμεν ὅτι τρίγωνον.

ὁμοίως δὲ καὶ ἐπὶ τῶν ἄλλων.

Τῇ μὲν οὖν καθόλου θεωροῦμεν τὰ ἐν μέρει, τῇ δ' οἰκείᾳ

οὐκ ἴσμεν, ὥστ' ἐνδέχεται καὶ ἀπατᾶσθαι περὶ αὐτά,

πλὴν οὐκ ἐναντίως, ἀλλ' ἔχειν μὲν τὴν καθόλου, ἀπατᾶσθαι

30 δὲ τὴν κατὰ μέρος. ὁμοίως οὖν καὶ ἐπὶ τῶν προειρημένων·

οὐ γὰρ ἐναντία ἡ κατὰ τὸ μέσον ἀπάτη τῇ κατὰ τὸν

συλλογισμὸν ἐπιστήμῃ, οὐδ' ἡ καθ' ἑκάτερον τῶν μέσων ὑπόληψις.

οὐδὲν δὲ κωλύει εἰδότα καὶ ὅτι τὸ Α ὅλῳ τῷ Β

ὑπάρχει καὶ πάλιν τοῦτο τῷ Γ, οἰηθῆναι μὴ ὑπάρχειν τὸ

35 Α τῷ Γ, οἷον ὅτι πᾶσα ἡμίονος ἄτοκος καὶ αὕτη ἡμίονος

οἴεσθαι κύειν ταύτην· οὐ γὰρ ἐπίσταται ὅτι τὸ Α τῷ Γ, μὴ

συνθεωρῶν τὸ καθ' ἑκάτερον. ὥστε δῆλον ὅτι καὶ εἰ τὸ μὲν

οἶδε τὸ δὲ μὴ οἶδεν, ἀπατηθήσεται· ὅπερ ἔχουσιν αἱ καθόλου

πρὸς τὰς κατὰ μέρος ἐπιστήμας. οὐδὲν γὰρ τῶν αἰσθητῶν

1Consequently if again he thinks that A belongs to nothing to which C belongs, he thinks that A does not belong to some of that to which B belongs; but if he thinks that A belongs to everything to which B belongs, and again thinks that A does not belong to some of that to which B belongs, 5these beliefs are wholly or partially contrary. In this way then it is not possible to think; but nothing prevents a man thinking one premiss of each syllogism of both premisses of one of the two syllogisms: e.g. A belongs to all B, and B to D, and again A belongs to no C. An error of this kind is similar to the error into which we fall concerning particulars: e.g. 10if A belongs to all B, and B to all C, A will belong to all C. If then a man knows that A belongs to everything to which B belongs, he knows that A belongs to C. But nothing prevents his being ignorant that C exists; e.g. let A stand for two right angles, B for triangle, C for a particular diagram of a triangle. 15A man might think that C did not exist, though he knew that every triangle contains two right angles; consequently he will know and not know the same thing at the same time. For the expression 'to know that every triangle has its angles equal to two right angles' is ambiguous, meaning to have the knowledge either of the universal or of the particulars. Thus then he knows that C contains two right angles with a knowledge of the universal, 20but not with a knowledge of the particulars; consequently his knowledge will not be contrary to his ignorance. The argument in the Meno that learning is recollection may be criticized in a similar way. For it never happens that a man starts with a foreknowledge of the particular, but along with the process of being led to see the general principle he receives a knowledge of the particulars, by an act (as it were) of recognition. For 25we know some things directly; e.g. that the angles are equal to two right angles, if we know that the figure is a triangle. Similarly in all other cases.
By a knowledge of the universal then we see the particulars, but we do not know them by the kind of knowledge which is proper to them; consequently it is possible that we may make mistakes about them, but not that we should have the knowledge and error that are contrary to one another: rather we have the knowledge of the universal 30but make a mistake in apprehending the particular. Similarly in the cases stated above. The error in respect of the middle term is not contrary to the knowledge obtained through the syllogism, nor is the thought in respect of one middle term contrary to that in respect of the other. Nothing prevents a man who knows both that A belongs to the whole of B, and that B again belongs to C, thinking that A does not belong to C, 35e.g. knowing that every mule is sterile and that this is a mule, and thinking that this animal is with foal: for he does not know that A belongs to C, unless he considers the two propositions together. So it is evident that if he knows the one and does not know the other, he will fall into error. And this is the relation of knowledge of the universal to knowledge of the particular.

67b

1 ἔξω τῆς αἰσθήσεως γενόμενον ἴσμεν, οὐδ' ἂν ᾐσθημένοι

τυγχάνωμεν, εἰ μὴ ὡς τῷ καθόλου καὶ τῷ ἔχειν τὴν

οἰκείαν ἐπιστήμην, ἀλλ' οὐχ ὡς τῷ ἐνεργεῖν. τὸ γὰρ ἐπίστασθαι

λέγεται τριχῶς, ἢ ὡς τῇ καθόλου ἢ ὡς τῇ οἰκείᾳ

5 ἢ ὡς τῷ ἐνεργεῖν, ὥστε καὶ τὸ ἠπατῆσθαι τοσαυταχῶς. οὐδὲν

οὖν κωλύει καὶ εἰδέναι καὶ ἠπατῆσθαι περὶ ταὐτό, πλὴν οὐκ

ἐναντίως. ὅπερ συμβαίνει καὶ τῷ καθ' ἑκατέραν εἰδότι τὴν

πρότασιν καὶ μὴ ἐπεσκεμμένῳ πρότερον. ὑπολαμβάνων γὰρ

κύειν τὴν ἡμίονον οὐκ ἔχει τὴν κατὰ τὸ ἐνεργεῖν ἐπιστήμην,

10 οὐδ' αὖ διὰ τὴν ὑπόληψιν ἐναντίαν ἀπάτην τῇ ἐπιστήμῃ·

συλλογισμὸς γὰρ ἡ ἐναντία ἀπάτη τῇ καθόλου.

Ὁ δ' ὑπολαμβάνων τὸ ἀγαθῷ εἶναι κακῷ εἶναι, τὸ

αὐτὸ ὑπολήψεται ἀγαθῷ εἶναι καὶ κακῷ. ἔστω γὰρ τὸ μὲν

ἀγαθῷ εἶναι ἐφ' οὗ Α, τὸ δὲ κακῷ εἶναι ἐφ' οὗ Β, πάλιν

15 δὲ τὸ ἀγαθῷ εἶναι ἐφ' οὗ Γ. ἐπεὶ οὖν ταὐτὸν ὑπολαμβάνει

τὸ Β καὶ τὸ Γ, καὶ εἶναι τὸ Γ τὸ Β ὑπολήψεται, καὶ

πάλιν τὸ Β τὸ Α εἶναι ὡσαύτως, ὥστε καὶ τὸ Γ τὸ Α.

ὥσπερ γὰρ εἰ ἦν ἀληθές, καθ' οὗ τὸ Γ, τὸ Β, καὶ καθ'

οὗ τὸ Β, τὸ Α, καὶ κατὰ τοῦ Γ τὸ Α ἀληθὲς ἦν, οὕτω καὶ

20 ἐπὶ τοῦ ὑπολαμβάνειν. ὁμοίως δὲ καὶ ἐπὶ τοῦ εἶναι· ταὐτοῦ

γὰρ ὄντος τοῦ Γ καὶ Β, καὶ πάλιν τοῦ Β καὶ Α, καὶ τὸ Γ

τῷ Α ταὐτὸν ἦν· ὥστε καὶ ἐπὶ τοῦ δοξάζειν ὁμοίως. ἆρ' οὖν

τοῦτο μὲν ἀναγκαῖον, εἴ τις δώσει τὸ πρῶτον; ἀλλ' ἴσως ἐκεῖνο

ψεῦδος, τὸ ὑπολαβεῖν τινὰ κακῷ εἶναι τὸ ἀγαθῷ εἶναι,

25 εἰ μὴ κατὰ συμβεβηκός· πολλαχῶς γὰρ ἐγχωρεῖ τοῦθ'

ὑπολαμβάνειν. ἐπισκεπτέον δὲ τοῦτο βέλτιον.

1For we know no sensible thing, once it has passed beyond the range of our senses, even if we happen to have perceived it, except by means of the universal and the possession of the knowledge which is proper to the particular, but without the actual exercise of that knowledge. For to know is used in three senses: it may mean either to have knowledge of the universal or to have knowledge proper to the matter in hand 5or to exercise such knowledge: consequently three kinds of error also are possible. Nothing then prevents a man both knowing and being mistaken about the same thing, provided that his knowledge and his error are not contrary. And this happens also to the man whose knowledge is limited to each of the premisses and who has not previously considered the particular question. For when he thinks that the mule is with foal he has not the knowledge in the sense of its actual exercise, 10nor on the other hand has his thought caused an error contrary to his knowledge: for the error contrary to the knowledge of the universal would be a syllogism.
But he who thinks the essence of good is the essence of bad will think the same thing to be the essence of good and the essence of bad. Let A stand for the essence of good and B for the essence of bad, 15and again C for the essence of good. Since then he thinks B and C identical, he will think that C is B, and similarly that B is A, consequently that C is A. For just as we saw that if B is true of all of which C is true, and A is true of all of which B is true, A is true of C, 20similarly with the word 'think'. Similarly also with the word 'is'; for we saw that if C is the same as B, and B as A, C is the same as A. Similarly therefore with 'opine'. Perhaps then this is necessary if a man will grant the first point. But presumably that is false, that any one could suppose the essence of good to be the essence of bad, 25save incidentally. For it is possible to think this in many different ways. But we must consider this matter better.

Book 2,Chapter 22 (67b27–68b7)

Ὅταν δ' ἀντιστρέφῃ τὰ ἄκρα, ἀνάγκη καὶ τὸ μέσον

ἀντιστρέφειν πρὸς ἄμφω. εἰ γὰρ τὸ Α κατὰ τοῦ Γ διὰ τοῦ

Β ὑπάρχει, εἰ ἀντιστρέφει καὶ ὑπάρχει, ᾧ τὸ Α, παντὶ

30 τὸ Γ, καὶ τὸ Β τῷ Α ἀντιστρέψει καὶ ὑπάρξει, ᾧ τὸ Α,

παντὶ τὸ Β διὰ μέσου τοῦ Γ· καὶ τὸ Γ τῷ Β ἀντιστρέψει

διὰ μέσου τοῦ Α. καὶ ἐπὶ τοῦ μὴ ὑπάρχειν ὡσαύτως, οἷον

εἰ τὸ Β τῷ Γ ὑπάρχει, τῷ δὲ Β τὸ Α οὐχ ὑπάρχει, οὐδὲ

τὸ Α τῷ Γ οὐχ ὑπάρξει. εἰ δὴ τὸ Β τῷ Α ἀντιστρέφει,

35 καὶ τὸ Γ τῷ Α ἀντιστρέψει. ἔστω γὰρ τὸ Β μὴ ὑπάρχον

τῷ Α· οὐδ' ἄρα τὸ Γ· παντὶ γὰρ τῷ Γ τὸ Β ὑπῆρχεν.

καὶ εἰ τῷ Β τὸ Γ ἀντιστρέφει, καὶ τὸ Α ἀντιστρέψει· καθ'

οὗ γὰρ ἅπαντος τὸ Β, καὶ τὸ Γ. καὶ εἰ τὸ Γ <καὶ> πρὸς τὸ Α

ἀντιστρέφει, καὶ τὸ Β ἀντιστρέψει. ᾧ γὰρ τὸ Β,

27Whenever the extremes are convertible it is necessary that the middle should be convertible with both. For if A belongs to C through B, then if A and C are convertible 30and C belongs everything to which A belongs, B is convertible with A, and B belongs to everything to which A belongs, through C as middle, and C is convertible with B through A as middle. Similarly if the conclusion is negative, e.g. if B belongs to C, but A does not belong to B, neither will A belong to C. If then B is convertible with A, 35C will be convertible with A. Suppose B does not belong to A; neither then will C: for ex hypothesi B belonged to all C. And if C is convertible with B, B is convertible also with A, for C is said of that of all of which B is said. And if C is convertible in relation to A and to B, B also is convertible in relation to A. For C belongs to that to which B belongs: but C does not belong to that to which A belongs.

68a

1 τὸ Γ· ᾧ δὲ τὸ Α, τὸ Γ οὐχ ὑπάρχει. καὶ μόνον τοῦτο

ἀπὸ τοῦ συμπεράσματος ἄρχεται, τὰ δ' ἄλλα οὐχ ὁμοίως

καὶ ἐπὶ τοῦ κατηγορικοῦ συλλογισμοῦ. Πάλιν εἰ τὸ Α καὶ

τὸ Β ἀντιστρέφει, καὶ τὸ Γ καὶ τὸ Δ ὡσαύτως, ἅπαντι δ'

5 ἀνάγκη τὸ Α ἢ τὸ Γ ὑπάρχειν, καὶ τὸ Β καὶ Δ οὕτως ἕξει

ὥστε παντὶ θάτερον ὑπάρχειν. ἐπεὶ γὰρ ᾧ τὸ Α, τὸ Β, καὶ

ᾧ τὸ Γ, τὸ Δ, παντὶ δὲ τὸ Α ἢ τὸ Γ καὶ οὐχ ἅμα, φανερὸν

ὅτι καὶ τὸ Β ἢ τὸ Δ παντὶ καὶ οὐχ ἅμα [οἷον ...

γεγονέναι]· δύο γὰρ συλλογισμοὶ σύγκεινται. πάλιν εἰ παντὶ

μὲν τὸ Α ἢ τὸ Β καὶ τὸ Γ ἢ τὸ Δ, ἅμα δὲ μὴ ὑπάρχει, εἰ ἀντιστρέφει

τὸ Α καὶ τὸ Γ, καὶ τὸ Β καὶ τὸ Δ ἀντιστρέφει. εἰ

γὰρ τινὶ μὴ ὑπάρχει τὸ Β, ᾧ τὸ Δ, δῆλον ὅτι τὸ Α ὑπάρχει.

15 εἰ δὲ τὸ Α, καὶ τὸ Γ· ἀντιστρέφει γάρ. ὥστε ἅμα τὸ Γ καὶ

ὍτανδὲτὸΑὅλῳτῷΒ Δ. τοῦτο δ' ἀδύνατον. <οἷον εἰ τὸ ἀγένητον ἄφθαρτον καὶτῷΓ

τὸ ἄφθαρτον ἀγένητον, ἀνάγκη τὸ γενόμενον φθαρτὸν καὶ τὸ

10 φθαρτὸν γεγονέναι>.

Ὅταν δὲ τὸ Α ὅλῳ τῷ Β καὶ τῷ Γ

ὑπάρχῃ καὶ μηδενὸς ἄλλου κατηγορῆται, ὑπάρχῃ δὲ καὶ

τὸ Β παντὶ τῷ Γ, ἀνάγκη τὸ Α καὶ Β ἀντιστρέφειν· ἐπεὶ

γὰρ κατὰ μόνων τῶν Β Γ λέγεται τὸ Α, κατηγορεῖται δὲ

20 τὸ Β καὶ αὐτὸ αὑτοῦ καὶ τοῦ Γ, φανερὸν ὅτι καθ' ὧν τὸ Α,

καὶ τὸ Β λεχθήσεται πάντων πλὴν αὐτοῦ τοῦ Α. πάλιν ὅταν

τὸ Α καὶ τὸ Β ὅλῳ τῷ Γ ὑπάρχῃ, ἀντιστρέφῃ δὲ τὸ Γ

τῷ Β, ἀνάγκη τὸ Α παντὶ τῷ Β ὑπάρχειν· ἐπεὶ γὰρ παντὶ

τῷ Γ τὸ Α, τὸ δὲ Γ τῷ Β διὰ τὸ ἀντιστρέφειν, καὶ τὸ Α

25 παντὶ τῷ Β. Ὅταν δὲ δυοῖν ὄντοιν τὸ Α τοῦ Β αἱρετώτερον

ᾖ, ὄντων ἀντικειμένων, καὶ τὸ Δ τοῦ Γ ὡσαύτως,

εἰ αἱρετώτερα τὰ Α Γ τῶν Β Δ, τὸ Α τοῦ Δ αἱρετώτερον.

ὁμοίως γὰρ διωκτὸν τὸ Α καὶ φευκτὸν τὸ Β (ἀντικείμενα

γάρ), καὶ τὸ Γ τῷ Δ (καὶ γὰρ ταῦτα ἀντίκειται). εἰ οὖν

30 τὸ Α τῷ Δ ὁμοίως αἱρετόν, καὶ τὸ Β τῷ Γ φευκτόν· ἑκάτερον

γὰρ ἑκατέρῳ ὁμοίως, φευκτὸν διωκτῷ. ὥστε καὶ τὰ

ἄμφω τὰ Α Γ τοῖς Β Δ. ἐπεὶ δὲ μᾶλλον, οὐχ οἷόν τε

ὁμοίως· καὶ γὰρ ἂν τὰ Β Δ ὁμοίως ἦσαν. εἰ δὲ τὸ Δ τοῦ Α

αἱρετώτερον, καὶ τὸ Β τοῦ Γ ἧττον φευκτόν· τὸ γὰρ ἔλαττον

35 τῷ ἐλάττονι ἀντίκειται. αἱρετώτερον δὲ τὸ μεῖζον ἀγαθὸν

καὶ ἔλαττον κακὸν ἢ τὸ ἔλαττον ἀγαθὸν καὶ μεῖζον

κακόν· καὶ τὸ ἅπαν ἄρα, τὸ Β Δ, αἱρετώτερον τοῦ Α Γ.

νῦν δ' οὐκ ἔστιν. τὸ Α ἄρα αἱρετώτερον τοῦ Δ, καὶ τὸ Γ ἄρα

τοῦ Β ἧττον φευκτόν. εἰ δὴ ἕλοιτο πᾶς ὁ ἐρῶν κατὰ τὸν

40 ἔρωτα τὸ Α τὸ οὕτως ἔχειν ὥστε χαρίζεσθαι, καὶ τὸ μὴ

χαρίζεσθαι τὸ ἐφ' οὗ Γ, ἢ τὸ χαρίζεσθαι τὸ ἐφ' οὗ Δ, καὶ

1And this alone starts from the conclusion; the preceding moods do not do so as in the affirmative syllogism. Again if A and B are convertible, and similarly C and D, and 5if A or C must belong to anything whatever, then B and D will be such that one or other belongs to anything whatever. For since B belongs to that to which A belongs, and D belongs to that to which C belongs, and since A or C belongs to everything, but not together, it is clear that B or D belongs to everything, but not together. For example if that which is uncreated is incorruptible and that which is incorruptible is uncreated, it is necessary that what is created should be corruptible and what is corruptible should have been created. For two syllogisms have been put together. Again if A or B belongs to everything and if C or D belongs to everything, but they cannot belong together, then when A and C are convertible B and D are convertible. For if B does not belong to something to which D belongs, it is clear that A belongs to it. 10But if A then C: for they are convertible. Therefore C and D belong together. But this is impossible. When A belongs to the whole of B and to C and is affirmed of nothing else, and B also belongs to all C, it is necessary that A and B should be convertible: for since A is said of B and C only, and B is affirmed 20both of itself and of C, it is clear that B will be said of everything of which A is said, except A itself. Again when A and B belong to the whole of C, and C is convertible with B, it is necessary that A should belong to all B: for since A belongs to all C, and C to B by conversion, 25A will belong to all B.
When, of two opposites A and B, A is preferable to B, and similarly D is preferable to C, then if A and C together are preferable to B and D together, A must be preferable to D. For A is an object of desire to the same extent as B is an object of aversion, since they are opposites: and C is similarly related to D, since they also are opposites. If then 30A is an object of desire to the same extent as D, B is an object of aversion to the same extent as C (since each is to the same extent as each-the one an object of aversion, the other an object of desire). Therefore both A and C together, and B and D together, will be equally objects of desire or aversion. But since A and C are preferable to B and D, A cannot be equally desirable with D; for then B along with D would be equally desirable with A along with C. But if D is preferable to A, then B must be less an object of aversion than C: 35for the less is opposed to the less. But the greater good and lesser evil are preferable to the lesser good and greater evil: the whole BD then is preferable to the whole AC. But ex hypothesi this is not so. A then is preferable to D, and C consequently is less an object of aversion than B. If then every lover in virtue of his love would prefer A, 40viz. that the beloved should be such as to grant a favour, and yet should not grant it (for which C stands), to the beloved's granting the favour (represented by D) without being such as to grant it (represented by B), it is clear that A (being of such a nature) is preferable to granting the favour.

68b

1 τὸ μὴ τοιοῦτον εἶναι οἷον χαρίζεσθαι τὸ ἐφ' οὗ Β, δῆλον ὅτι

τὸ Α τὸ τοιοῦτον εἶναι αἱρετώτερόν ἐστιν ἢ τὸ χαρίζεσθαι. τὸ

ἄρα φιλεῖσθαι τῆς συνουσίας αἱρετώτερον κατὰ τὸν ἔρωτα.

μᾶλλον ἄρα ὁ ἔρως ἐστὶ τῆς φιλίας ἢ τοῦ συνεῖναι. εἰ δὲ

5 μάλιστα τούτου, καὶ τέλος τοῦτο. τὸ ἄρα συνεῖναι ἢ οὐκ ἔστιν

ὅλως ἢ τοῦ φιλεῖσθαι ἕνεκεν· καὶ γὰρ αἱ ἄλλαι ἐπιθυμίαι

καὶ τέχναι οὕτως.

1To receive affection then is preferable in love to sexual intercourse. Love then is more dependent on friendship than on intercourse. 5And if it is most dependent on receiving affection, then this is its end. Intercourse then either is not an end at all or is an end relative to the further end, the receiving of affection. And indeed the same is true of the other desires and arts.

Book 2,Chapter 23 (68b8–37)

Πῶς μὲν οὖν ἔχουσιν οἱ ὅροι κατὰ τὰς ἀντιστροφὰς

καὶ τὸ αἱρετώτεροι ἢ φευκτότεροι εἶναι, φανερόν· ὅτι δ' οὐ

10 μόνον οἱ διαλεκτικοὶ καὶ ἀποδεικτικοὶ συλλογισμοὶ διὰ

τῶν προειρημένων γίνονται σχημάτων, ἀλλὰ καὶ οἱ ῥητορικοὶ

καὶ ἁπλῶς ἡτισοῦν πίστις καὶ ἡ καθ' ὁποιανοῦν μέθοδον,

νῦν ἂν εἴη λεκτέον. ἅπαντα γὰρ πιστεύομεν ἢ διὰ συλλογισμοῦ

ἢ ἐξ ἐπαγωγῆς.

15 Ἐπαγωγὴ μὲν οὖν ἐστι καὶ ὁ ἐξ ἐπαγωγῆς συλλογισμὸς

τὸ διὰ τοῦ ἑτέρου θάτερον ἄκρον τῷ μέσῳ συλλογίσασθαι,

οἷον εἰ τῶν Α Γ μέσον τὸ Β, διὰ τοῦ Γ δεῖξαι τὸ Α

τῷ Β ὑπάρχον· οὕτω γὰρ ποιούμεθα τὰς ἐπαγωγάς. οἷον

ἔστω τὸ Α μακρόβιον, τὸ δ' ἐφ' ᾧ Β τὸ χολὴν μὴ ἔχον,

20 ἐφ' ᾧ δὲ Γ τὸ καθ' ἕκαστον μακρόβιον, οἷον ἄνθρωπος καὶ

ἵππος καὶ ἡμίονος. τῷ δὴ Γ ὅλῳ ὑπάρχει τὸ Α (πᾶν γὰρ

τὸ Γ μακρόβιον)· ἀλλὰ καὶ τὸ Β, τὸ μὴ ἔχειν χολήν,

παντὶ ὑπάρχει τῷ Γ. εἰ οὖν ἀντιστρέφει τὸ Γ τῷ Β καὶ μὴ

ὑπερτείνει τὸ μέσον, ἀνάγκη τὸ Α τῷ Β ὑπάρχειν. δέδεικται

25 γὰρ πρότερον ὅτι ἂν δύο ἄττα τῷ αὐτῷ ὑπάρχῃ καὶ

πρὸς θάτερον αὐτῶν ἀντιστρέφῃ τὸ ἄκρον, ὅτι τῷ ἀντιστρέφοντι

καὶ θάτερον ὑπάρξει τῶν κατηγορουμένων. δεῖ δὲ νοεῖν

τὸ Γ τὸ ἐξ ἁπάντων τῶν καθ' ἕκαστον συγκείμενον· ἡ γὰρ

ἐπαγωγὴ διὰ πάντων.

30 Ἔστι δ' ὁ τοιοῦτος συλλογισμὸς τῆς πρώτης καὶ ἀμέσου

προτάσεως· ὧν μὲν γὰρ ἔστι μέσον, διὰ τοῦ μέσου ὁ

συλλογισμός, ὧν δὲ μὴ ἔστι, δι' ἐπαγωγῆς. καὶ τρόπον

τινὰ ἀντίκειται ἡ ἐπαγωγὴ τῷ συλλογισμῷ· ὁ μὲν γὰρ διὰ

τοῦ μέσου τὸ ἄκρον τῷ τρίτῳ δείκνυσιν, ἡ δὲ διὰ τοῦ τρίτου

35 τὸ ἄκρον τῷ μέσῳ. φύσει μὲν οὖν πρότερος καὶ γνωριμώτερος

ὁ διὰ τοῦ μέσου συλλογισμός, ἡμῖν δ' ἐναργέστερος ὁ

διὰ τῆς ἐπαγωγῆς.

8It is clear then how the terms are related in conversion, and in respect of being in a higher degree objects of aversion or of desire. We must now state that not 10only dialectical and demonstrative syllogisms are formed by means of the aforesaid figures, but also rhetorical syllogisms and in general any form of persuasion, however it may be presented. For every belief comes either through syllogism or from induction.
15Now induction, or rather the syllogism which springs out of induction, consists in establishing syllogistically a relation between one extreme and the middle by means of the other extreme, e.g. if B is the middle term between A and C, it consists in proving through C that A belongs to B. For this is the manner in which we make inductions. For example let A stand for long-lived, B for bileless, and 20C for the particular long-lived animals, e.g. man, horse, mule. A then belongs to the whole of C: for whatever is bileless is long-lived. But B also ('not possessing bile') belongs to all C. If then C is convertible with B, and the middle term is not wider in extension, it is necessary that A should belong to B. For it has already been proved 25that if two things belong to the same thing, and the extreme is convertible with one of them, then the other predicate will belong to the predicate that is converted. But we must apprehend C as made up of all the particulars. For induction proceeds through an enumeration of all the cases.
30Such is the syllogism which establishes the first and immediate premiss: for where there is a middle term the syllogism proceeds through the middle term; when there is no middle term, through induction. And in a way induction is opposed to syllogism: for the latter proves the major term to belong to the third term by means of the middle, the former 35proves the major to belong to the middle by means of the third. In the order of nature, syllogism through the middle term is prior and better known, but syllogism through induction is clearer to us.

Book 2,Chapter 24 (68b38–69a19)

Παράδειγμα δ' ἐστὶν ὅταν τῷ μέσῳ τὸ ἄκρον ὑπάρχον

δειχθῇ διὰ τοῦ ὁμοίου τῷ τρίτῳ. δεῖ δὲ καὶ τὸ μέσον

40 τῷ τρίτῳ καὶ τὸ πρῶτον τῷ ὁμοίῳ γνώριμον εἶναι ὑπάρχον.

οἷον ἔστω τὸ Α κακόν, τὸ δὲ Β πρὸς ὁμόρους ἀναιρεῖσθαι

38We have an 'example' when the major term is proved to belong to the middle by means of a term which resembles the third. It ought to 40be known both that the middle belongs to the third term, and that the first belongs to that which resembles the third.

69a

1 πόλεμον, ἐφ' ᾧ δὲ Γ τὸ Ἀθηναίους πρὸς Θηβαίους, τὸ δ'

ἐφ' ᾧ Δ Θηβαίους πρὸς Φωκεῖς. ἐὰν οὖν βουλώμεθα δεῖξαι

ὅτι τὸ Θηβαίοις πολεμεῖν κακόν ἐστι, ληπτέον ὅτι τὸ πρὸς

τοὺς ὁμόρους πολεμεῖν κακόν. τούτου δὲ πίστις ἐκ τῶν

5 ὁμοίων, οἷον ὅτι Θηβαίοις ὁ πρὸς Φωκεῖς. ἐπεὶ οὖν τὸ πρὸς

τοὺς ὁμόρους κακόν, τὸ δὲ πρὸς Θηβαίους πρὸς ὁμόρους ἐστί,

φανερὸν ὅτι τὸ πρὸς Θηβαίους πολεμεῖν κακόν. ὅτι μὲν οὖν

τὸ Β τῷ Γ καὶ τῷ Δ ὑπάρχει, φανερόν (ἄμφω γάρ ἐστι

πρὸς τοὺς ὁμόρους ἀναιρεῖσθαι πόλεμον), καὶ ὅτι τὸ Α τῷ

10 Δ (Θηβαίοις γὰρ οὐ συνήνεγκεν ὁ πρὸς Φωκεῖς πόλεμος)· ὅτι

δὲ τὸ Α τῷ Β ὑπάρχει, διὰ τοῦ Δ δειχθήσεται. τὸν αὐτὸν

δὲ τρόπον κἂν εἰ διὰ πλειόνων τῶν ὁμοίων ἡ πίστις γένοιτο

τοῦ μέσου πρὸς τὸ ἄκρον. φανερὸν οὖν ὅτι τὸ παράδειγμά

ἐστιν οὔτε ὡς μέρος πρὸς ὅλον οὔτε ὡς ὅλον πρὸς μέρος,

15 ἀλλ' ὡς μέρος πρὸς μέρος, ὅταν ἄμφω μὲν ᾖ ὑπὸ ταὐτό,

γνώριμον δὲ θάτερον. καὶ διαφέρει τῆς ἐπαγωγῆς, ὅτι ἡ

μὲν ἐξ ἁπάντων τῶν ἀτόμων τὸ ἄκρον ἐδείκνυεν ὑπάρχειν

τῷ μέσῳ καὶ πρὸς τὸ ἄκρον οὐ συνῆπτε τὸν συλλογισμόν,

τὸ δὲ καὶ συνάπτει καὶ οὐκ ἐξ ἁπάντων δείκνυσιν.

1For example let A be evil, B making war against neighbours, C Athenians against Thebans, D Thebans against Phocians. If then we wish to prove that to fight with the Thebans is an evil, we must assume that to fight against neighbours is an evil. Evidence of this is obtained from 5similar cases, e.g. that the war against the Phocians was an evil to the Thebans. Since then to fight against neighbours is an evil, and to fight against the Thebans is to fight against neighbours, it is clear that to fight against the Thebans is an evil. Now it is clear that B belongs to C and to D (for both are cases of making war upon one's neighbours) and that A belongs to 10D (for the war against the Phocians did not turn out well for the Thebans): but that A belongs to B will be proved through D. Similarly if the belief in the relation of the middle term to the extreme should be produced by several similar cases. Clearly then to argue by example is neither like reasoning from part to whole, nor like reasoning from whole to part, 15but rather reasoning from part to part, when both particulars are subordinate to the same term, and one of them is known. It differs from induction, because induction starting from all the particular cases proves (as we saw) that the major term belongs to the middle, and does not apply the syllogistic conclusion to the minor term, whereas argument by example does make this application and does not draw its proof from all the particular cases.

Book 2,Chapter 25 (69a20–36)

20 Ἀπαγωγὴ δ' ἐστὶν ὅταν τῷ μὲν μέσῳ τὸ πρῶτον δῆλον

ᾖ ὑπάρχον, τῷ δ' ἐσχάτῳ τὸ μέσον ἄδηλον μέν, ὁμοίως

δὲ πιστὸν ἢ μᾶλλον τοῦ συμπεράσματος· ἔτι ἂν ὀλίγα ᾖ

τὰ μέσα τοῦ ἐσχάτου καὶ τοῦ μέσου· πάντως γὰρ ἐγγύτερον

εἶναι συμβαίνει τῆς ἐπιστήμης. οἷον ἔστω τὸ Α τὸ διδακτόν,

25 ἐφ' οὗ Β ἐπιστήμη, τὸ Γ δικαιοσύνη. ἡ μὲν οὖν ἐπιστήμη ὅτι

διδακτόν, φανερόν· ἡ δ' ἀρετὴ εἰ ἐπιστήμη, ἄδηλον. εἰ οὖν

ὁμοίως ἢ μᾶλλον πιστὸν τὸ Β Γ τοῦ Α Γ, ἀπαγωγή ἐστιν·

ἐγγύτερον γὰρ τοῦ ἐπίστασθαι διὰ τὸ προσειληφέναι τὴν Α Β

ἐπιστήμην, πρότερον οὐκ ἔχοντας. ἢ πάλιν εἰ ὀλίγα τὰ μέσα

30 τῶν Β Γ· καὶ γὰρ οὕτως ἐγγύτερον τοῦ εἰδέναι. οἷον εἰ τὸ Δ

εἴη τετραγωνίζεσθαι, τὸ δ' ἐφ' ᾧ Ε εὐθύγραμμον, τὸ δ'

ἐφ' ᾧ Ζ κύκλος· εἰ τοῦ Ε Ζ ἓν μόνον εἴη μέσον, τὸ μετὰ

μηνίσκων ἴσον γίνεσθαι εὐθυγράμμῳ τὸν κύκλον, ἐγγὺς ἂν

εἴη τοῦ εἰδέναι. ὅταν δὲ μήτε πιστότερον ᾖ τὸ Β Γ τοῦ Α Γ μήτ'

35 ὀλίγα τὰ μέσα, οὐ λέγω ἀπαγωγήν. οὐδ' ὅταν ἄμεσον ᾖ τὸ

Β Γ· ἐπιστήμη γὰρ τὸ τοιοῦτον.

20By reduction we mean an argument in which the first term clearly belongs to the middle, but the relation of the middle to the last term is uncertain though equally or more probable than the conclusion; or again an argument in which the terms intermediate between the last term and the middle are few. For in any of these cases it turns out that we approach more nearly to knowledge. For example let A stand for what can be taught, 25B for knowledge, C for justice. Now it is clear that knowledge can be taught: but it is uncertain whether virtue is knowledge. If now the statement BC is equally or more probable than Ac, we have a reduction: for we are nearer to knowledge, since we have taken a new term, being so far without knowledge that A belongs to C. Or again suppose that the terms intermediate 30between B and C are few: for thus too we are nearer knowledge. For example let D stand for squaring, E for rectilinear figure, F for circle. If there were only one term intermediate between E and F (viz. that the circle is made equal to a rectilinear figure by the help of lunules), we should be near to knowledge. But when BC is not more probable than AC, and the intermediate terms are not few, 35I do not call this reduction: nor again when the statement BC is immediate: for such a statement is knowledge.

Book 2,Chapter 26 (69a37–70a9)

Ἔνστασις δ' ἐστὶ πρότασις προτάσει ἐναντία. διαφέρει

δὲ τῆς προτάσεως, ὅτι τὴν μὲν ἔνστασιν ἐνδέχεται εἶναι ἐπὶ

μέρους, τὴν δὲ πρότασιν ἢ ὅλως οὐκ ἐνδέχεται ἢ οὐκ ἐν τοῖς

37An objection is a premiss contrary to a premiss. It differs from a premiss, because it may be particular, but a premiss either cannot be particular at all or not in universal syllogisms.

69b

1 καθόλου συλλογισμοῖς. φέρεται δὲ ἡ ἔνστασις διχῶς καὶ

διὰ δύο σχημάτων, διχῶς μὲν ὅτι ἢ καθόλου ἢ ἐν μέρει

πᾶσα ἔνστασις, ἐκ δύο δὲ σχημάτων ὅτι ἀντικείμεναι φέρονται

τῇ προτάσει, τὰ δ' ἀντικείμενα ἐν τῷ πρώτῳ καὶ

5 τῷ τρίτῳ σχήματι περαίνονται μόνοις. ὅταν γὰρ ἀξιώσῃ

παντὶ ὑπάρχειν, ἐνιστάμεθα ἢ ὅτι οὐδενὶ ἢ ὅτι τινὶ οὐχ ὑπάρχει·

τούτων δὲ τὸ μὲν μηδενὶ ἐκ τοῦ πρώτου σχήματος, τὸ

δὲ τινὶ μὴ ἐκ τοῦ ἐσχάτου. οἷον ἔστω τὸ Α μίαν εἶναι ἐπιστήμην,

ἐφ' ᾧ τὸ Β ἐναντία. προτείναντος δὴ μίαν εἶναι τῶν

10 ἐναντίων ἐπιστήμην, ἢ ὅτι ὅλως οὐχ ἡ αὐτὴ τῶν ἀντικειμένων

ἐνίσταται, τὰ δ' ἐναντία ἀντικείμενα, ὥστε γίνεται τὸ πρῶτον

σχῆμα, ἢ ὅτι τοῦ γνωστοῦ καὶ ἀγνώστου οὐ μία· τοῦτο δὲ τὸ

τρίτον· κατὰ γὰρ τοῦ Γ, τοῦ γνωστοῦ καὶ ἀγνώστου, τὸ μὲν

ἐναντία εἶναι ἀληθές, τὸ δὲ μίαν αὐτῶν ἐπιστήμην εἶναι ψεῦδος.

15 πάλιν ἐπὶ τῆς στερητικῆς προτάσεως ὡσαύτως. ἀξιοῦντος

γὰρ μὴ εἶναι μίαν τῶν ἐναντίων, ἢ ὅτι πάντων τῶν ἀντικειμένων

ἢ ὅτι τινῶν ἐναντίων ἡ αὐτὴ λέγομεν, οἷον ὑγιεινοῦ

καὶ νοσώδους· τὸ μὲν οὖν πάντων ἐκ τοῦ πρώτου, τὸ δὲ τινῶν

ἐκ τοῦ τρίτου σχήματος. Ἁπλῶς γὰρ ἐν πᾶσι καθόλου μὲν

20 ἐνιστάμενον ἀνάγκη πρὸς τὸ καθόλου τῶν προτεινομένων τὴν

ἀντίφασιν εἰπεῖν, οἷον εἰ μὴ τὴν αὐτὴν ἀξιοῖ τῶν ἐναντίων,

πάντων εἰπόντα τῶν ἀντικειμένων μίαν. οὕτω δ' ἀνάγκη τὸ

πρῶτον εἶναι σχῆμα· μέσον γὰρ γίνεται τὸ καθόλου πρὸς

τὸ ἐξ ἀρχῆς. ἐν μέρει δέ, πρὸς ὅ ἐστι καθόλου καθ' οὗ λέγεται

25 ἡ πρότασις, οἷον γνωστοῦ καὶ ἀγνώστου μὴ τὴν αὐτήν·

τὰ γὰρ ἐναντία καθόλου πρὸς ταῦτα. καὶ γίνεται τὸ τρίτον

σχῆμα· μέσον γὰρ τὸ ἐν μέρει λαμβανόμενον, οἷον τὸ γνωστὸν

καὶ τὸ ἄγνωστον. ἐξ ὧν γὰρ ἔστι συλλογίσασθαι τοὐναντίον,

ἐκ τούτων καὶ τὰς ἐνστάσεις ἐπιχειροῦμεν λέγειν. διὸ

30 καὶ ἐκ μόνων τούτων τῶν σχημάτων φέρομεν· ἐν μόνοις γὰρ

οἱ ἀντικείμενοι συλλογισμοί· διὰ γὰρ τοῦ μέσου οὐκ ἦν καταφατικῶς.

ἔτι δὲ κἂν λόγου δέοιτο πλείονος ἡ διὰ τοῦ μέσου

σχήματος, οἷον εἰ μὴ δοίη τὸ Α τῷ Β ὑπάρχειν διὰ

τὸ μὴ ἀκολουθεῖν αὐτῷ τὸ Γ. τοῦτο γὰρ δι' ἄλλων προτάσεων

35 δῆλον· οὐ δεῖ δὲ εἰς ἄλλα ἐκτρέπεσθαι τὴν ἔνστασιν,

ἀλλ' εὐθὺς φανερὰν ἔχειν τὴν ἑτέραν πρότασιν. [διὸ καὶ τὸ

σημεῖον ἐκ μόνου τούτου τοῦ σχήματος οὐκ ἔστιν.]

Ἐπισκεπτέον δὲ καὶ περὶ τῶν ἄλλων ἐνστάσεων, οἷον

περὶ τῶν ἐκ τοῦ ἐναντίου καὶ τοῦ ὁμοίου καὶ τοῦ κατὰ δόξαν, καὶ

1An objection is brought in two ways and through two figures; in two ways because every objection is either universal or particular, by two figures because objections are brought in opposition to the premiss, and opposites can be proved only in the first and third figures. 5If a man maintains a universal affirmative, we reply with a universal or a particular negative; the former is proved from the first figure, the latter from the third. For example let stand for there being a single science, B for contraries. 10If a man premises that contraries are subjects of a single science, the objection may be either that opposites are never subjects of a single science, and contraries are opposites, so that we get the first figure, or that the knowable and the unknowable are not subjects of a single science: this proof is in the third figure: for it is true of C (the knowable and the unknowable) that they are contraries, and it is false that they are the subjects of a single science.
15Similarly if the premiss objected to is negative. For if a man maintains that contraries are not subjects of a single science, we reply either that all opposites or that certain contraries, e.g. what is healthy and what is sickly, are subjects of the same science: the former argument issues from the first, the latter from the third figure.
In general if a man urges a universal objection 20he must frame his contradiction with reference to the universal of the terms taken by his opponent, e.g. if a man maintains that contraries are not subjects of the same science, his opponent must reply that there is a single science of all opposites. Thus we must have the first figure: for the term which embraces the original subject becomes the middle term.
If the objection is particular, the objector must frame his contradiction with reference to a term relatively to which the subject of his opponent's premiss is universal, e.g. he will point out 25that the knowable and the unknowable are not subjects of the same science: 'contraries' is universal relatively to these. And we have the third figure: for the particular term assumed is middle, e.g. the knowable and the unknowable. Premisses from which it is possible to draw the contrary conclusion are what we start from when we try to make objections. 30Consequently we bring objections in these figures only: for in them only are opposite syllogisms possible, since the second figure cannot produce an affirmative conclusion.
Besides, an objection in the middle figure would require a fuller argument, e.g. if it should not be granted that A belongs to B, because C does not follow B. This can be made clear only by other premisses. 35But an objection ought not to turn off into other things, but have its new premiss quite clear immediately. For this reason also this is the only figure from which proof by signs cannot be obtained.

70a

1 εἰ τὴν ἐν μέρει ἐκ τοῦ πρώτου ἢ τὴν στερητικὴν ἐκ τοῦ μέσου

δυνατὸν λαβεῖν.

10 <Ἐνθύμημα δὲ ἐστὶ συλλογισμὸς ἐξ εἰκότων ἢ σημείων,>

1We must consider later the other kinds of objection, namely the objection from contraries, from similars, and from common opinion, and inquire whether a particular objection cannot be elicited from the first figure or a negative objection from the second.

Book 2,Chapter 27 (70a10–70b38)

εἰκὸς

δὲ καὶ σημεῖον οὐ ταὐτόν ἐστιν, ἀλλὰ τὸ μὲν εἰκός ἐστι πρότασις

ἔνδοξος· ὃ γὰρ ὡς ἐπὶ τὸ πολὺ ἴσασιν οὕτω γινόμενον ἢ μὴ

5 γινόμενον ἢ ὂν ἢ μὴ ὄν, τοῦτ' ἐστὶν εἰκός, οἷον τὸ μισεῖν τοὺς

φθονοῦντας ἢ τὸ φιλεῖν τοὺς ἐρωμένους. σημεῖον δὲ βούλεται

εἶναι πρότασις ἀποδεικτικὴ ἢ ἀναγκαία ἢ ἔνδοξος· οὗ γὰρ

ὄντος ἔστιν ἢ οὗ γενομένου πρότερον ἢ ὕστερον γέγονε τὸ

πρᾶγμα, τοῦτο σημεῖόν ἐστι τοῦ γεγονέναι ἢ εἶναι. [ἐνθύμημα

. . . σημείων] λαμβάνεται δὲ τὸ σημεῖον τριχῶς, ὁσαχῶς

καὶ τὸ μέσον ἐν τοῖς σχήμασιν· ἢ γὰρ ὡς ἐν τῷ πρώτῳ

ἢ ὡς ἐν τῷ μέσῳ ἢ ὡς ἐν τῷ τρίτῳ, οἷον τὸ μὲν δεῖξαι κύουσαν

διὰ τὸ γάλα ἔχειν ἐκ τοῦ πρώτου σχήματος· μέσον

15 γὰρ τὸ γάλα ἔχειν. ἐφ' ᾧ τὸ Α κύειν, τὸ Β γάλα ἔχειν,

γυνὴ ἐφ' ᾧ Γ. τὸ δ' ὅτι οἱ σοφοὶ σπουδαῖοι, Πιττακὸς γὰρ

σπουδαῖος, διὰ τοῦ ἐσχάτου. ἐφ' ᾧ Α τὸ σπουδαῖον, ἐφ' ᾧ

Β οἱ σοφοί, ἐφ' ᾧ Γ Πιττακός. ἀληθὲς δὴ καὶ τὸ Α καὶ

τὸ Β τοῦ Γ κατηγορῆσαι· πλὴν τὸ μὲν οὐ λέγουσι διὰ τὸ εἰδέναι,

20 τὸ δὲ λαμβάνουσιν. τὸ δὲ κύειν, ὅτι ὠχρά, διὰ τοῦ

μέσου σχήματος βούλεται εἶναι· ἐπεὶ γὰρ ἕπεται ταῖς κυούσαις

τὸ ὠχρόν, ἀκολουθεῖ δὲ καὶ ταύτῃ, δεδεῖχθαι οἴονται

ὅτι κύει. τὸ ὠχρὸν ἐφ' οὗ τὸ Α, τὸ κύειν ἐφ' οὗ Β, γυνὴ

ἐφ' οὗ Γ. Ἐὰν μὲν οὖν ἡ μία λεχθῇ πρότασις, σημεῖον γίνεται

25 μόνον, ἐὰν δὲ καὶ ἡ ἑτέρα προσληφθῇ, συλλογισμός,

οἷον ὅτι Πιττακὸς ἐλευθέριος· οἱ γὰρ φιλότιμοι ἐλευθέριοι,

Πιττακὸς δὲ φιλότιμος. ἢ πάλιν ὅτι οἱ σοφοὶ ἀγαθοί· Πιττακὸς

γὰρ ἀγαθός, ἀλλὰ καὶ σοφός. οὕτω μὲν οὖν γίνονται

συλλογισμοί, πλὴν ὁ μὲν διὰ τοῦ πρώτου σχήματος ἄλυτος,

30 ἂν ἀληθὴς ᾖ (καθόλου γάρ ἐστιν), ὁ δὲ διὰ τοῦ ἐσχάτου

λύσιμος, κἂν ἀληθὲς ᾖ τὸ συμπέρασμα, διὰ τὸ μὴ εἶναι

καθόλου μηδὲ πρὸς τὸ πρᾶγμα τὸν συλλογισμόν· οὐ γὰρ

εἰ Πιττακὸς σπουδαῖος, διὰ τοῦτο καὶ τοὺς ἄλλους ἀνάγκη

σοφούς. ὁ δὲ διὰ τοῦ μέσου σχήματος ἀεὶ καὶ πάντως λύσιμος·

35 οὐδέποτε γὰρ γίνεται συλλογισμὸς οὕτως ἐχόντων

τῶν ὅρων· οὐ γὰρ εἰ ἡ κύουσα ὠχρά, ὠχρὰ δὲ καὶ ἥδε,

κύειν ἀνάγκη ταύτην. ἀληθὲς μὲν οὖν ἐν ἅπασιν ὑπάρξει τοῖς

σημείοις, διαφορὰς δ' ἔχουσι τὰς εἰρημένας.

10A probability and a sign are not identical, but a probability is a generally approved proposition: what men know to happen or not to happen, to be or not to be, 5for the most part thus and thus, is a probability, e.g. 'the envious hate', 'the beloved show affection'. A sign means a demonstrative proposition necessary or generally approved: for anything such that when it is another thing is, or when it has come into being the other has come into being before or after, is a sign of the other's being or having come into being. Now an enthymeme is a syllogism starting from probabilities or signs, and a sign may be taken in three ways, corresponding to the position of the middle term in the figures. For it may be taken as in the first figure or the second or the third. For example the proof that a woman is with child because she has milk is in the first figure: for to have milk is the middle term. 15Let A represent to be with child, B to have milk, C woman. The proof that wise men are good, since Pittacus is good, comes through the last figure. Let A stand for good, B for wise men, C for Pittacus. It is true then to affirm both A and B of C: only men do not say the latter, because they know it, though they state the former. 20The proof that a woman is with child because she is pale is meant to come through the middle figure: for since paleness follows women with child and is a concomitant of this woman, people suppose it has been proved that she is with child. Let A stand for paleness, B for being with child, C for woman. Now if the one proposition is stated, we have only a sign, 25but if the other is stated as well, a syllogism, e.g. 'Pittacus is generous, since ambitious men are generous and Pittacus is ambitious.' Or again 'Wise men are good, since Pittacus is not only good but wise.' In this way then syllogisms are formed, only that which proceeds through the first figure 30is irrefutable if it is true (for it is universal), that which proceeds through the last figure is refutable even if the conclusion is true, since the syllogism is not universal nor correlative to the matter in question: for though Pittacus is good, it is not therefore necessary that all other wise men should be good. But the syllogism which proceeds through the middle figure is always refutable in any case: 35for a syllogism can never be formed when the terms are related in this way: for though a woman with child is pale, and this woman also is pale, it is not necessary that she should be with child. Truth then may be found in signs whatever their kind, but they have the differences we have stated.

70b

1 Ἢ δὴ οὕτω διαιρετέον τὸ σημεῖον, τούτων δὲ τὸ μέσον

τεκμήριον ληπτέον (τὸ γὰρ τεκμήριον τὸ εἰδέναι ποιοῦν φασὶν

εἶναι, τοιοῦτο δὲ μάλιστα τὸ μέσον), ἢ τὰ μὲν ἐκ τῶν

ἄκρων σημεῖον λεκτέον, τὰ δ' ἐκ τοῦ μέσου τεκμήριον· ἐνδοξότατον

5 γὰρ καὶ μάλιστα ἀληθὲς τὸ διὰ τοῦ πρώτου σχήματος.

Τὸ δὲ φυσιογνωμονεῖν δυνατόν ἐστιν, εἴ τις δίδωσιν ἅμα

μεταβάλλειν τὸ σῶμα καὶ τὴν ψυχὴν ὅσα φυσικά ἐστι

παθήματα· μαθὼν γὰρ ἴσως μουσικὴν μεταβέβληκέ τι τὴν

10 ψυχήν, ἀλλ' οὐ τῶν φύσει ἡμῖν ἐστὶ τοῦτο τὸ πάθος, ἀλλ'

οἷον ὀργαὶ καὶ ἐπιθυμίαι τῶν φύσει κινήσεων. εἰ δὴ τοῦτό τε

δοθείη καὶ ἓν ἑνὸς σημεῖον εἶναι, καὶ δυναίμεθα λαμβάνειν

τὸ ἴδιον ἑκάστου γένους πάθος καὶ σημεῖον, δυνησόμεθα φυσιογνωμονεῖν.

εἰ γάρ ἐστιν ἰδίᾳ τινὶ γένει ὑπάρχον ἀτόμῳ

15 πάθος, οἷον τοῖς λέουσιν ἀνδρεία, ἀνάγκη καὶ σημεῖον εἶναί

τι· συμπάσχειν γὰρ ἀλλήλοις ὑπόκειται. καὶ ἔστω τοῦτο τὸ

μεγάλα τὰ ἀκρωτήρια ἔχειν· ὃ καὶ ἄλλοις ὑπάρχειν γένεσι

μὴ ὅλοις ἐνδέχεται. τὸ γὰρ σημεῖον οὕτως ἴδιόν ἐστιν,

ὅτι ὅλου γένους ἴδιόν ἐστι [πάθος], καὶ οὐ μόνου ἴδιον,

20 ὥσπερ εἰώθαμεν λέγειν. ὑπάρξει δὴ καὶ ἐν ἄλλῳ γένει

τοῦτο, καὶ ἔσται ἀνδρεῖος [ὁ] ἄνθρωπος καὶ ἄλλο τι ζῷον.

ἕξει ἄρα τὸ σημεῖον· ἓν γὰρ ἑνὸς ἦν. εἰ τοίνυν ταῦτ' ἐστί,

καὶ δυνησόμεθα τοιαῦτα σημεῖα συλλέξαι ἐπὶ τούτων τῶν

ζῴων ἃ μόνον ἓν πάθος ἔχει τι ἴδιον, ἕκαστον δ' ἔχει σημεῖον,

25 ἐπείπερ ἓν ἔχειν ἀνάγκη, δυνησόμεθα φυσιογνωμονεῖν.

εἰ δὲ δύο ἔχει ἴδια ὅλον τὸ γένος, οἷον ὁ λέων ἀνδρεῖον

καὶ μεταδοτικόν, πῶς γνωσόμεθα πότερον ποτέρου σημεῖον

τῶν ἰδίᾳ ἀκολουθούντων σημείων; ἢ εἰ ἄλλῳ τινὶ μὴ ὅλῳ

ἄμφω, καὶ ἐν οἷς μὴ ὅλοις ἑκάτερον, ὅταν τὸ μὲν ἔχῃ τὸ

30 δὲ μή· εἰ γὰρ ἀνδρεῖος μὲν ἐλευθέριος δὲ μή, ἔχει δὲ τῶν

δύο τοδί, δῆλον ὅτι καὶ ἐπὶ τοῦ λέοντος τοῦτο σημεῖον τῆς

ἀνδρείας. Ἔστι δὴ τὸ φυσιογνωμονεῖν τῷ ἐν τῷ πρώτῳ σχήματι

τὸ μέσον τῷ μὲν πρώτῳ ἄκρῳ ἀντιστρέφειν, τοῦ δὲ τρίτου

ὑπερτείνειν καὶ μὴ ἀντιστρέφειν, οἷον ἀνδρεία τὸ Α, τὰ

35 ἀκρωτήρια μεγάλα ἐφ' οὗ Β, τὸ δὲ Γ λέων. ᾧ δὴ τὸ Γ,

τὸ Β παντί, ἀλλὰ καὶ ἄλλοις. ᾧ δὲ τὸ Β, τὸ Α παντὶ

καὶ οὐ πλείοσιν, ἀλλ' ἀντιστρέφει· εἰ δὲ μή, οὐκ ἔσται ἓν

ἑνὸς σημεῖον.

1We must either divide signs in the way stated, and among them designate the middle term as the index (for people call that the index which makes us know, and the middle term above all has this character), or else we must call the arguments derived from the extremes signs, that derived from the middle term the index: for that which is proved through the first figure 5is most generally accepted and most true.
It is possible to infer character from features, if it is granted that the body and the soul are changed together by the natural affections: I say 'natural', for though perhaps by learning music a man has made some change in his soul, 10this is not one of those affections which are natural to us; rather I refer to passions and desires when I speak of natural emotions. If then this were granted and also that for each change there is a corresponding sign, and we could state the affection and sign proper to each kind of animal, we shall be able to infer character from features. For if there is an affection which belongs properly to an individual kind, 15e.g. courage to lions, it is necessary that there should be a sign of it: for ex hypothesi body and soul are affected together. Suppose this sign is the possession of large extremities: this may belong to other kinds also though not universally. For the sign is proper in the sense stated, because the affection is proper to the whole kind, though not proper to it alone, 20according to our usual manner of speaking. The same thing then will be found in another kind, and man may be brave, and some other kinds of animal as well. They will then have the sign: for ex hypothesi there is one sign corresponding to each affection. If then this is so, and we can collect signs of this sort in these animals which have only one affection proper to them-but each affection has its sign, 25since it is necessary that it should have a single sign-we shall then be able to infer character from features. But if the kind as a whole has two properties, e.g. if the lion is both brave and generous, how shall we know which of the signs which are its proper concomitants is the sign of a particular affection? Perhaps if both belong to some other kind though not to the whole of it, and if, in those kinds in which each is found though not in the whole of their members, some members possess one of the affections and not the other: e.g. 30if a man is brave but not generous, but possesses, of the two signs, large extremities, it is clear that this is the sign of courage in the lion also. To judge character from features, then, is possible in the first figure if the middle term is convertible with the first extreme, but is wider than the third term and not convertible with it: e.g. let A stand for courage, 35B for large extremities, and C for lion. B then belongs to everything to which C belongs, but also to others. But A belongs to everything to which B belongs, and to nothing besides, but is convertible with B: otherwise, there would not be a single sign correlative with each affection.