Azione Romana

Analitici primiLibro II

Aristotele (384–322 a.C.) · Analytica priora · Ἀναλυτικὰ πρότερα · Bekker 24a–70b

Libro II, capitolo 1 Recapitulation.—Of the Conclusions of certain Syllogisms.52b38–53b3

Inglese

52b38We have already explained the number of the figures, the character and number of the premisses, when and how 52b40a syllogism is formed ;! further what we must look for when 53arefuting 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.1, Since some syllogisms are universal, others 53a5particular, all 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, e. g. if 53a10A has been proved to belong 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.

53a15This 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; 53a20e.g. if the conclusion AB is 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. In the second 53a25figure 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 53a30clear by means of the syllogism. And yet B does not belong to “,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.

53a34But in particular syllogisms there will be no necessity of 53a35inferring 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 Land 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, but not through the 53a40preceding syllogism. Similarly in the other figures. That which is subordinate to the conclusion cannot be proved; 53bthe 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.

Note del traduttore
  1. 1 i, 1-26. 2, 27-31.

Libro II, capitolo 2 On a true Conclusion deduced from false Premises in the first Figure.53b4–55b2

Inglese

53b4It is possible for the premisses of the syllogism to be 53b5true, or 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: why 53b10this is so will be explained in the sequel.1

53b11First 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 the same 53b15thing 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, and two relations of subject and 53b20predicate 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 negative 53b25syllogisms: it is not possible to prove a false conclusion from true premisses.

53b26But 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,2 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.3 53b30(1) Let A belong to the whole of C, but to none of the B, 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 53b35conclusion is true: for 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 A, e.g. if 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.4 Consequently if one term is taken 53b40to 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 54awill be true. (2) A similar proof may be given if each premiss is partially false.

54a2(3) But if one only of the premisses is false, when the first premiss is wholly false, e.g. AZ, 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’ the contrary of 54a5the 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: for A belonged to none of the Cs, 54a10since A belonged to nothing to which B belonged, and B belonged to all C. Similarly there cannot be a truce 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 AB is also assumed, viz. that A belongs to nothing to which B belongs: here the conclusion must be false. For A will 54a15belong to all C, since 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.

54a18(4) But if the premiss is not wholly false, a true conclusion is possible. For if A belongs to all C and to some B, and if B 54a20belongs 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. For5 it is possible that A 54a25should belong to some B and 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 A will belong to no C.

54a29(5) But if the premiss AB, which is assumed, is wholly true, and the premiss BC is wholly false, a true syllogism will be 54a30possible: for nothing prevents A belonging to all B and to all C, though B belongs to no C, e.g. these 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. If then it is assumed that A belongs to all B and B to all C, the conclusion will be true, although the premiss 54a35BC is wholly false. Similarly 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 54bto 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.

54b3(6) And if the premiss BC is not wholly false but in part only, even so the conclusion may be true. For nothing 54b5prevents A belonging to 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 hypothesis is true. Similarly belongs to some instance of ‘speculative’. If then it should 54b15be assumed that A belongs to no B, and B to all C, A will belong to no C: and this ex hypothesis? is true.

54b17In particular syllogisms it is possible when the first premiss is wholly false, and the other true, that the conclusion should be true; also when the first premiss is false 54b20in 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 then6 snow 54b25is taken as middle, and animal as first term, and it is assumed that A belongs to the whole of B, and B to some C, then the premiss AB 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 54b30of B, but not to some C, although 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.

54b35(8) If 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. animal to something beautiful and to something great, and beautiful7 belonging to something great. If then A is assumed to belong to all B, and B to some C, the premiss AB will be 55apartially false, the premiss BC will be true, and the con-elusion true. Similarly if the premiss AB is negative. For the same terms will serve, and in the same positions, to prove the point.8

55a5(9) Again if the 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, 55a10the 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: for 55a15animal belongs to no number and not to some white things,9 and number belongs to nothing white. If then number is taken as middle, and it is assumed that A belongs to no A, and B to some C, then A will not belong to some C, which ex hypothesis is true. And the premiss AB is true, the premiss BC false.

55a19(10) Also if the premiss AB is partially false, and the premiss 55a20BC 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 55a25no black thing. If 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.

55a28(11) Also though both premisses are false the conclusion may be true. For it is possible that A may belong to no B 55a30and 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, the 55a35conclusion 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. animal belongs to every swan, and not to some black things, and swan belongs to nothing 55a40black. Consequently if it is assumed that A belongs to 55bno B, and B to some C, then A does not belong to some C, The conclusion then is true, but the premisses are false.

Note del traduttore
  1. 1 i.e. the conclusion of the original syllogism, which would have to become the major premiss of the further syllogism required. A particular major premiss yields no conclusion (in the first figure). ἢ 578 40-> 17.
  2. 2 Omit ἀλλὰ τῆς δευτέρας in l. 28 with codd. Bu.
  3. 3 The following cases are discussed in the sequel: Universal premisses. 53b30-5421 Both premisses wholly false, conclusion true. 54° 1, 2 Both premisses partly false, conclusion true. 543 2-18 Major wholly false, minor true, conclusion false. 54° 18-28 Major partly false, minor true, conclusion true. 54a28->2 Major true, minor wholly false, conclusion true. 54b2-16 Major true, minor partly false, conclusion true. One premiss particular. 54b21-35 Major wholly false, minor true, conclusion true. 54 35-55°4 Major partly false, minor true, conclusion true. 55° 4-19 Major true, minor wholly false, conclusion true. 55a19-28 Major partly false, minor wholly false, conclusion true. 55a28->2 Both premisses wholly false, conclusion true.
  4. 4 ΝῸ B (men) are A (animals). All C (stones) are B (men). . No C (stones) are A (animals).
  5. 5 1oif the premiss AZ 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
  6. 6 1 Omit 6Ans in l. 1. 20 with A, B, C, and Waitz.
  7. 7 οὐ in l. 24 (Bekker) is a misprint for οὖν, J See note 43b3.
  8. 8 viz. that a true conclusion may follow if one premiss is partially false, the other true.
  9. 9 Read in l. 15 τινὶ οὔ, which seems to have been read by Phil. No B (number) is A (animal). (True.) Some C (white) is B (number). (False.) ἐν Some C (white) is not A (animal). (True.)

Libro II, capitolo 3 The same in the middle Figure.55b3–56b3

Inglese

55b3In 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 55b5are wholly false; when each is partially false; when 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 55b10wholly false, the other partially true.1 For (I) if 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. 55b15Similarly if A belongs to all B and to no C: for we shall have the same syllogism.

55b17(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 and man, and 55b20no 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.

55b24(3) Also if one premiss is partially false, the other wholly true. For it is possible that A should belong to some B 55b25and to all C, though B belongs to no C, e.g. animal to some white things and to every raven, though white belongs ἴο πὸ 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. Similarly 55b30if the negative statement is transposed:2 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,3 while B belongs to no C, e.g. animal belongs to some white things, but to no 55b35pitch, and 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.

55b38(4) And if both the premisses are partially false, the conclusion may be true. For it is possible that A should 55b40belong to some B and to some C, and B to no C. g. animal to some white things and to some black things, though white 56abelongs 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.

56a5It is clear also that our thesis holds in particular syllogisms. For (5) nothing prevents A belonging to all B and to some C, though 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 56a10A belongs to no B and to some C, the 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 56a15white things, and lifeless will not belong to some white things.4 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 A 56a20following? 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, 56a25but the particular false. Similarly if the premiss which is stated universally is affirmative. For it is possible that A should 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 to the 56a30whole of B, but does not belong to some C, the universal premiss is true, the particular false, and the conclusion true.

56a32(6) It is clear too that though both premisses are false they may yield a true conclusion, since it is possible that should belong both to B and to C as wholes,5 though B 56a35does not follow some C. For6 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. For7 it is possible that A should follow no B and all C, though B does not 56a40belong to some C, e.g. animal follows no science but every man, though science does not follow every man. If then A 56bis assumed to belong to the whole of B, and not to follow some C, the premisses are false but the conclusion is true.

Note del traduttore
  1. 1 The possible combinations of premisses in which there is some element of falsity are: (1) Wholly false with wholly false. (2) True with wholly false. (3) Partly false with partly false. (4) True with partly false. (5) Wholly false with partly false. ἐπί τι ἑκατέρας seems, in the light of 56b20-33, to mean the third (and not the fifth) of these cases, which is also expressed by καὶ ef ἀμφότεραι ἐπί τι ψευδεῖς. Waltz would excise the latter clause for this reason, and καὶ ef ἡ μὲν ὕλη ψευδὴς ἡ δ᾽ ἐπί τι ἀληθής because (αἱ ἐπί τι ἀληθής does not occur elsewhere in Aristotle, (4) it must mean either (i) the same as ‘partly false’, so that case (5) is meant, a case entirely ignored by Aristotle throughout cc. 2-4, and therefore not to be expected here, or (11) something else, in which case Aristotle illogically omits all the other combinations which include one ‘partly true’ premiss. To (a) it may be replied that ἐπί τι ἀληθής is justified by the use of its opposite ἁπλῶς ἀληθῆς 1. 7, which Waitz does not reject (cf. ὅλη ἀληθὴς 1. 17, &c.). To (6) it may be replied that the clause plainly does indicate case (5) and that this case ts expressly dealt with in the discussion of the first figure, 55b19-28. It is true that this case is omitted in the detailed discussion of the second figure, where with reference to universal syllogisms (1) is discussed in 55b10-16, (2) in 55b16-23, (4) in 55a23-38, (3) in 55a38-56°4, and with reference to particular syllogisms (2) is discussed in 56a5-32, (1) in 56a32-P3. But similarly (3) is omitted in the discussion of particular syllogisms in the first figure. Aristotle does not attempt to work out all the possibilities. There remains the repetition involved in ἐπί re ἑκατέρας and εἰ ἀμφότεραι ἐπί τι ψευδεῖς, It is quite possible that through confusion Aristotle wrote the passage as it stands; if anything 15 to go It seems better to excise ἐπί re ἑκατέρας as introduced by imitation of c. 4, 56b5.
  2. 2 i.e. treated as minor instead of major premiss.
  3. 3 i.e. not to any C.
  4. 4 Read οὔ for οὐχ ὑπάρχει in l. 15 with C,. The sense requires a negative, though this has little MS. support. All B (lifeless) is A (animal). (False.) Some C (white) is not A (animal). (True.) .. Some C (white) is not B (lifeless). (True.) .. Some C (white) is not 8 (lifeless). (True.)
  5. 5 The sense requires something like the reading implied in l. 34 by Boethius’ translation, viz. τῷ μὲν ὅλῳ τῷ δὲ μηδενί, in place of ὅλῳ. No fis A. (False.) “Some Cis A. (False.) “. Some Cis not δι, (True.) But the confusion may be in Aristotle.
  6. 6 The following cases are discussed in the sequel: Both premisses universal,
  7. 7 56b9-20 Both premisses wholly false, conclusion true.

Libro II, capitolo 4 Similar Observations upon a true Conclusion from false Premises in the third Figure.56b4–57b17

Inglese

56b4In the last figure a true conclusion may come through 56b5what is false, alike 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.1 For (I) nothing prevents 56b10neither A nor B from belonging to any C, while 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. For it is 56b15possible that B should belong to no C, but A to all C, and that A 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 to234 all C, and A to no C, A will not belong to some B: and the 56b20conclusion is true, though the premisses are false.

56b21(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 belong 56b25to 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, beautiful 56b30belongs 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.

56b33(3) Similarly if one of the premisses assumed is wholly false, the other wholly true. For it is possible that both A and 56b35B should 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, and the conclusion 56b40true. Similarly if the statement BC is false, the. statement AC true, the conclusion may be true. The 57asame terms will serve for the proof.5 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. animal belongs to every swan,6 black to no swan, and black to some animals. Consequently if it Is assumed that A and B belong to every C, the premiss C 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.

57a9(4) Again if one premiss is wholly true, the other partly 57a10false, 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, the premiss AC partly false, 57a15the conclusion true. Similarly if of the premisses assumed A 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, and A to some C, 57a20and, when they are so, that A should not belong to all B, therefore if 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, it 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.

57a29(5) It is clear also in the case of particular syllogisms7 that 57a30a 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 57a35that what belongs to some belongs to all. The same applies to negative statements.

57a36It 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 the 57a40conclusion may none the less be true; but it is not necessitated, 57bThe 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 cither, 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 that B 57b5should 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 A is white that C should not be white. And whenever it is necessary, since one of two things is, that 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, A will necessarily 57b15not 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.

Note del traduttore
  1. 1 56b20-33 Both premisses partly false, conclusion true.
  2. 2 56b33-5729 One premiss true, the other wholly false, conclusion true.
  3. 3 57a9-28 One premiss true, the other partly false, conclusion true. One premiss particular.
  4. 4 57a29-35 Same situation as when both premisses are universal.
  5. 5 ‘Black—swan—lifeless’, which follow in the MSS. at 1. I, are not ‘the same terms’, and owe their origin to the (lost) commentary of Alexander, who saw that ‘the same terms’—animal, white, swan— will not serve Aristotle’s turn—i.e. if they are as before respectively major, minor, and middle term.
  6. 6 ? Omit μὲν in l. 4 with B and Waitz. Η 2
  7. 7 i.e. syllogisms having one premiss particular.

Libro II, capitolo 5 Of Demonstration in a Circle, in the first Figure.57b18–58b12

Inglese

57b18Circular and reciprocal proof means proof by means of the conclusion, i.e. by converting one of the premisses 57b20simply and inferring the other premiss which was assumed in the original syllogism1: 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 57b25syllogism the converse was assumed, viz. 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 57b30proof is not circular: for 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 57b35or the middle to the first. If the terms are convertible, it is possible to demonstrate everything reciprocally, e. g. if A and B and C are convertible with one another. Suppose the proposition AC has been demonstrated through B as middle term, and again the proposition AB through the conclusion and the premiss PC converted, and similarly the 57b40proposition BC through the conclusion and the premiss AB 58aconverted. But it is necessary to prove both the premiss CL, 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 58a5relating B to A. Again 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 58a10reciprocally. If 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, 58a15the matter stands as we said above). But 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 A, by assuming that C is said of A, and C is proved of A through these premisses, so that we use the conclusion for 58a20the demonstration.

58a21In 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 58a25previously assumed) A 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’. But we must assume that B belongs to all of that to none of 58a30which A belongs. Let 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 58a35converse of one of the premisses, and deduce the remaining premiss.

58a36In 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 58a40universal, but the conclusion is not universal, and the proof must start from the conclusion and the other premiss. Further a syllogism cannot be made at all if the other 58bpremiss 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 58b5is retained, B 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 58b10the universal syllogism,2 i. c. B belongs to some of that to some of which A does not belong’: otherwise no syllogism results because the particular premiss is negative.

Note del traduttore
  1. 1 The sentence would be clearer if we could read λαβεῖν in l. 20.
  2. 2 Read δι᾽ ὅ in l. 7 with Buhle. ; ᾿ ον 2. Cf.%29. Omit with Δ, B, and Waitz in l. 8 μὲν and in l. 9 οὐκ ἔστι, διὰ προσλήψεως δ᾽ ἔστιν.

Libro II, capitolo 6 Of the same in the second Figure.58b13–38

Inglese

58b13In the second figure it is not possible to prove an affirmative proposition in this way, but a negative proposition 58b15may be proved. An affirmative proposition is 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 58b20B belongs to no C. If then it is assumed that B belongs to all A,1 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, 58b25consequently B belongs to no A: neither 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 is not universal, the universal premiss cannot be proved, for the same reason as we gave above,” but 58b30the particular premiss can 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: for 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,2 if it is assumed that A belongs to some of that to some of which B does not belong.

Note del traduttore
  1. 1 Omit τῷ δὲ Τ' μηδενί in l. 20 with A, B, and Waitz. 2.8 ,8,
  2. 2 (ἢ, 820.

Libro II, capitolo 7 Of the same in the third Figure.58b39–59a41

Inglese

58b39In the third figure, when both premisses are taken 58b40universally, it is not possible to prove them reciprocally: for that which is universal is proved through statements which 59aare 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. But if one premiss is universal, the other particular, proof of the latter will sometimes be possible, sometimes not. When both the 59a5premisses 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 P 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 59a10not been proved. And 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. But 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 Band 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, the other premiss can be proved. 59a20Let 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 59a25proved, except as before,1 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 C. If then it is assumed that C belongs to some of that to some of which A does not belong, it is necessary that C should belong to some of the Bs. In no other way is it possible by 59a30converting the universal premiss to prove the other: for in no other way can a syllogism be formed.

59a32It 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; if the con-elusion 59a35is 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 59a40is clear also that in 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.

Note del traduttore
  1. 1 58>o.

Libro II, capitolo 8 Of Conversion of Syllogisms in the first Figure.59b1–60a14

Inglese

59b1To convert a syllogism means to alter the conclusion and make another syllogism to prove that cither the extreme” cannot belong to the middle or the middle to the last1 term. For it is necessary, if the conclusion has been changed into its opposite and one of the premisses stands, that the other 59b5premiss should be destroyed. For 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’; 59b10by contrary opposition I mean the opposition of ‘to all’ to ‘to none’, and of ‘to some’ to ‘not to some'. Suppose that A has been proved of C, through B as middle term. If then it should be assumed that A belongs to no C, but to all P, 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, but not to all B. For 59b15(as we saw) the universal is not proved through the last figure.2 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 figure; since it is necessary to take both premisses in reference to 59b20the minor extreme. Similarly if the syllogism is negative. Suppose it has been proved that +! 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.

59b25If 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 to all C, but 59b30to 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, and B to 59b35all C, as was originally assumed, A will belong to some B.

59b36In 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 59b40the result is no longer, as in the universal syllogisms,’ a refutation in which the conclusion reached by conversion 60alacks universality, but no refutation at all. Suppose that A has been proved of some C. If 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. But neither can be refuted if the conclusion is converted into its contrary, For if A docs 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: for if A does 60a10not 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.

Note del traduttore
  1. 1 Cf. 58 22-7, 596-14.
  2. 2 Major term. 8. Minor. 1, 6. 1], 13-20, 23-4.

Libro II, capitolo 9 Of Conversion of Syllogisms in the second Figure.60a15–60b5

Inglese

60a15In 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, if the conclusion of 60a20the 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 Band 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. 60a25If B belongs to all C, and 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,1 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 60a30all B, A 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.

60a33If the syllogism is particular, when the conclusion is converted into its contrary neither premiss can be refuted, as also happened in the first figure,2 but if the conclusion is 60a35converted into its contradictory, both 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 Cand also not to some C. Again if 60a40belongs to some Cand A to some C, no syllogism will be possible: for neither of the premisses taken is universal. 60bConsequently 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 Cand A to some C, A will belong to some B. The same proof can be 60b5given if the universal statement is affirmative.

Note del traduttore
  1. 1 6. 2 i.e. by its contradictory.
  2. 2 59b39-607 1, 60a5-14.

Libro II, capitolo 10 Of the same in the third Figure.60b6–61a16

Inglese

60b6In 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 60b10some B, C 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. 60b15A similar proof can be given if 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.1 But if the conclusion is converted into its contradictory, both the 60b20premisses2 can be refuted. For if .J 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. For3 if A belongs to no B, and B to some C, A will not belong to some C: if dl 60b25belongs to no B, and to all C, B will belong to no C.

60b26Similarly 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,4 a syllogism could be made. Whenever then the contrary of the conclusion is assumed a syllogism will not 60b30be possible. For 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.5 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 60b35B to C, a 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 60b40to all B, and B to some C, it results that A belongs to some C: but it was supposed to belong to no C. Again if A 61abelongs to all B, and to no C, then B belongs to no C: but it was assumed to belong to some C. If 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.

61a5From 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 the premiss which concerns 61a10the minor extreme is always 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; the premiss which 61a15concerns the major is always refuted through the first figure, the premiss which concerns the minor through the middle figure.

Note del traduttore
  1. 1 26° 17-21, 278 4-12.
  2. 2 Read ἀντιστρέφηται in l. 19 (which Phil. seems to have read), and place the comma before ai προτάσεις with Waitz.
  3. 3 28b1-4, 15-297 10.
  4. 4 264 30-6.
  5. 5 6-8. T nab * i.e. in refutation of the premisses of a syllogism in the first figure.

Libro II, capitolo 11 Of Deduction to the Impossible in the first Figure.61a17–62a19

Inglese

61a17It 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 the con-elusion 61a20is 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 61a25contradictory has been agreed to already, but because it is clear that it is true.1 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 61a30belongs to no 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.

61a34All the problems can be proved per impossibile in all the 61a35figures, 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 B belongs to all ;D; thus we get 61a40the first figure. If then it is supposed that A does not belong to all B, no syllogism results whichever term the 61bassumed 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. Let this be impossible: it is false then that 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 in the first figure per impossibile.

61b10But 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):2 consequently if 61b15this 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.

61b19Again suppose that A belongs to some B, and let it have 61b20been assumed that C 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, we shall have a syllogism and 61b25an 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, if it 61b30does 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.

61b33To 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, and C to 61b35all 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 61b40not to all but 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; 62aconsequently it is true that A belongs to no B. But 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 62a5the hypothesis: for 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’ have the same 62a10meaning, the demonstration of both will be identical.

62a11It 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, the affirmation 62a15must 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.

Note del traduttore
  1. 1 j.e. in conversion we explicitly assume one premiss and the opposite of the conclusion, and thus form a syllogism: in reduction ad imposstbile we need not explicitly assume the original premiss which is the opposite of the conclusion of the new syllogism; we may treat Its truth as obvious.
  2. 2 Read ἔστω... A ll. 13, 14 in brackets, and omit the comma after ἀληθές, with Waitz.

Libro II, capitolo 12 Of the same in the second Figure.62a20–62b4

Inglese

62a20It 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 62a25that A belongs to all C. If 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 the problem 62a30in hand is not proved. For1 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.

62a33When 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 62a35Should belong to no B. Consequently, 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.2

62a38Again 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, 62a40consequently the hypothesis is false: A then will belong to no £.

62a42When A does not belong to all B, suppose it does belong 62bto 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.

Note del traduttore
  1. 1 Read ταὐτ᾽ ἔσται in }. 36.
  2. 2 61) 39-6278. 5. 428-32. Read ταὐτ᾽ ἔσται in l. 10 with cod. ἢ.

Libro II, capitolo 13 Of the same in the third Figure.62b5–28

Inglese

62b5Similarly 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 docs 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 62b10proved: for if the contrary is supposed, we shall have the same results as before.”

62b12But 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.

62b15When A belongs to no B, suppose “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 hypothesis 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.

62b19But this hypothesis must be made if we are to prove 62b20that A belongs not to all B. For if -l belongs to all B and C to some B, then Al 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.1

62b25It 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.

Note del traduttore
  1. 1 61b39-62° 8, Read ταύὐτ᾽ ἔσται in l. 23 with cod. ἢ.

Libro II, capitolo 14 Of the difference between the Ostensive, and the Deduction to the Impossible.62b29–63b21

Inglese

62b29Demonstration per impossibile differs from ostensive proof 62b30in 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 62b35conclusion. Also 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, 62b40and that which is proved per impossibile can be proved ostensively, through the same terms. Whenever the syllogism1 63ais 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. Whenever the syllogism is 63a5formed in the last figure, the truth will be found in the first and middle figures, if affirmative in the 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 that 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 d and to no B. And it is clear from these premisses that A belongs to no B. Similarly if A has been proved 63a15snot to belong to all B. For 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 A 63a20belongs to no B; and the original premisses that 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.

63a25Again 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. Similarly if it has been 63a30proved 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. If the 63a35syllogism 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.

63a40Again suppose it has been proved in the third figure that A belongs to all B. Then the hypothesis must have been 63bthat 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 63b5that C 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 that 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 63b10then 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.

63b12It is clear then that it is possible through the same terms to prove each of the problems ostensively as well.2 Similarly it will be possible if the syllogisms are ostensive to reduce 63b15them 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. per impossibile 63b20and ostensively, and it is not possible to separate one method from the other.

Note del traduttore
  1. 1 Omit the comma after ἀναιρεῖν in l. 30. 5. Omit ἀληθῶν in l. 32 with B, C, and Waitz. 1 Omit otk... σχήμασιν in l. 41 with the MSS, and Waitz. 5 i.e. the reduction ad zmpPossibile. ® i.e. the ostensive syllogism.
  2. 2 } 2 Omit cal... ἀδυνάτου in l. 13 with A, C, and Waitz.

Libro II, capitolo 15 Of the Method of concluding from Opposites in the several Figures.63b22–64b27

Inglese

63b22In 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. universal affirmative to universal 63b25negative, 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 good1, 63b30‘no science is good’; the others I call contradictories

63b31In 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 63b35negative: no 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.

63b40In the middle figure a syllogism can be made both of contradictories and of contraries. Let A stand for good, let 64aB 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 ‘every science is good’ 64a5one 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 a particular 64a10science 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. 64a15Consequently it is possible that contradictories may lead to a conclusion, though 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.

64a20In the third figure an affirmative syllogism can never be made out of opposite premisses, for the reason given in reference to the first figure;2 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 one should 64a25assume 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 64a30science, it results that some science is not science. The premisses are contrary if the terms are taken universally; if one is particular, they are contradictory.

64a33We must recognize that it is possible to take opposites in the way we said, viz. ‘all science is good’ and ‘no science is 64a35good’ 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 cither universal affirmative and negative, or universal 64a40affirmative and particular negative, or particular affirmative and universal negative, and the relations between 64bthe terms may be reversed; e.g. A 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 64b5clear in how many ways and in what figures a syllogism can be made by means of premisses which are opposed.

64b7It is clear too that from false premisses it is possible to draw a true conclusion, as has been said before,3 but it is not possible if the premisses are opposed. For the syllogism 64b10is always contrary to the 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, it is not odd. 64b15For 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,4 unless a self-contradictory 64b20premiss 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,”5 and then assuming ‘Medicine is a science, but none of it is supposition’ (which is the mode in which refutations are 64b25made), or we must argue from two syllogisms. In no other way than this, as was said before,6 is it possible that the premisses should be really contrary.

Note del traduttore
  1. 1 Elsewhere Aristotle sometimes expresses this by ἀντεφατικῶς ἀντι- κεῖσθαι.
  2. 2 6333.
  3. 3 Read BA in l. 28 with A, B, C, and Waitz. 3 viii. I. * cc. 2-4.
  4. 4 i.e. in such a way that our conclusion is formally affirmative.
  5. 5 Omit καὶ οὐχ ὑπόληψις in l. 23 with B, ἢ, and Waitz.
  6. 6 It has been shown that contrary premisses will not yield an affirmative self-contradictory conclusion in the first figure (63° 33) or in the third (64b20). In the second of course all conclusions are negative.

Libro II, capitolo 16 Of the “Petitio Principii,” or Begging the Question. *.64b28–65a37

Inglese

64b28To beg and assume the original question is a species of failure to demonstrate the problem proposed; but this 64b30happens 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, and other things 64b35by 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 not1 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 to make a transition to 64b40other things which would naturally be proved through the 65athesis proposed, and demonstrate it through them, e.g. if 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 “| by means of itself. This is what those persons do who suppose 65a5that they are constructing parallel straight lines: for 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.

65a10If 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, or if they are 65a15plainly convertible, or the one belongs to the other,2 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 described3 and effecting a reciprocal proof with three propositions.4

65a19Similarly if he should assume that B belongs to C, this 65a20being 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. 65a25proving that which is not self-evident by means of itself,

65a26If 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, the question may 65a30be begged in the middle and third figures in both ways,5 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;6 and both premisses do not beg the question indifferently (in a similar way the question may be begged in the middle figure *)7, because the terms in negative syllogisms 65a35are not convertible.8 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.

Note del traduttore
  1. 1 Read μὴ τὸ in l. 36 with A, B, C, and Waitz.
  2. 2 As genus to species.
  3. 3 In Il, 1-4.
  4. 4 Omit ὡς ἴῃ 1. 19 with A, B, C, and Waitz.
  5. 5 ταὐτὰ τῷ αὐτῷ and ταὐτὸν τοῖς αὐτοῖς are explained by ll. 14-23; they refer to petitio principii in the minor and major premiss respectively. Now from the forms and rules of the figures it follows that the former can arise only in fig. I (affirmatively) and fig. II (negatively), the latter in figs. I and III (affirmatively and negatively). Thus the statement that both can occur in figs. I] and III is not, in its natural meaning, true.
  6. 6 ra αὐτὰ ἀπὸ τοῦ αὐτοῦ is apparently meant to cover the case of ταὐτὸν ἀπὸ τῶν αὐτῶν, the stress being on ἀπό, Strictly τὰ αὐτὰ ἀπὸ τοῦ αὐτοῦ is found only in the second figure.
  7. 7 ὡσαΐτως. .. μέσῳ in l. 34 is parenthetical.
  8. 8 ie. terms negatively related are not convertible, therefore it must be the terms in the affirmative premiss that are convertible, and the petitio principit must be in the negative premiss. It will be noticed that both in accuracy and in form this paragraph falls below the general level of the P7tor Analytics. It bears clear marks of haste.

Libro II, capitolo 17 A Consideration of the Syllogism, in which it is argued, that the false does not happen—“on account of this,” παρὰ τοῦτο συμβαίνειν, τὸ ψεδος.65a38–66a15

Inglese

65a38The objection that ‘this is not the reason why the result is false’, which we frequently make in argument, is made 65a40primarily in the case of a reduction ad impossibile, to rebut the proposition which was being proved by the reduction. 65bFor 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 denies1 is not assumed as a premiss. Further when anything is refuted ostensively by the terms ABC, it cannot be objected that the syllogism does not depend2 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 65b10only be used in the case of a reduction 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 from middle terms to an 65b15impossible 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 reduction 65b20ad impossibile: for 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 65b25down that A belongs to B, B 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 Cand C to D, the false conclusion would not depend on the original hypothesis. Or again trace the connexion upwards; e.g. suppose 65b30that A belongs to B, E 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 65b35connected with 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. Similarly when the syllogisms 65b40are negative.

66a1It 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.3 For if it were laid down that A belongs not to B but to K, and 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 66a10result; but 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 than two right 66a15angles.

Note del traduttore
  1. 1 Read τίθησι ὃ ἀντίφησιν in l. 3 with Ay, B, C, and Waitz.
  2. 2 Soph, El. 167b21-36.
  3. 3 Mark of interrogation after ψεῦδος in 1, 3 (Waitz). ? i.e. that A belongs to D. 5 53 11-25.

Libro II, capitolo 18 Of false Reasoning.66a16–24

Inglese

66a16A 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 was proved) a false syllogism cannot be drawn from true premisses. 66a20But 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.

Citato nell'enciclopedia: PETIZIONE DI PRINCIPIO

Libro II, capitolo 19 Of the Prevention of a Catasylllogism.66a25–66b3

Inglese

66a25In 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 66a30conclusion, is 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.

66a33That which we urge men to beware of in their admissions, they ought in attack to try to conceal. This will be possible 66a35first, 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.1 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 whether D belongs to E, instead of asking 66a40whether B belongs to C; after that he may ask whether B 66bbelongs to C, and so on. If the syllogism is drawn through one middle term, he ought to begin with that: in this way he will most likely deceive his opponent.

Note del traduttore
  1. 1 Read pddurra dpeoa in 1, 37 with A, B, C., and Waitz, and perhaps Phil.

Libro II, capitolo 20 Of the Elenchus.66b4–17

Inglese

66b4Since we know when a syllogism can be formed and how 66b5its terms must be related, it 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 what is laid 66b10down 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 saw1) when all the terms are negative: therefore no refutation is possible. For if a refutation were possible, a syllogism must 66b15be possible; although 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.

Note del traduttore
  1. 1 Read εἴη in l. 10 with cod. m, nz, and Waitz. 2.41} 6.

Libro II, capitolo 21 Of Deception, as to Supposition—κατὰ τὴν ὑπόληψιν.66b18–67b26

Inglese

66b19It sometimes happens that just as we are deceived in the arrangement of the terms,1 so error may arise in our thought 66b20about them, e.g. if it is possible that the same predicate should belong to more than one subject immediately,2 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, but A to no C, and C to all 66b25D, 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 scries; 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 66b30that A belongs to I), and 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.

66b35In the former case, where 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 Band 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. For if he thinks 66b40that A belongs to everything to which B belongs, and he 67aknows that B belongs to D, then he knows that A belongs to D. Consequently 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;3 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 67a5which B belongs, these 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 or both premisses of one of the two syllogisms: e.g. d 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. if 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. A man might think that C did not 67a15exist, 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, 67a20but not with a knowledge of the particulars; consequently his knowledge will not be contrary to his ignorance. The argument in the Meno4 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 we know some things directly; e.g. that the angles are equal to two right angles, 67a25if we know that the figure is a triangle. Similarly in all other cases.

67a26By 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 67a30but make a mistake in apprehending the particular. Similarly in the cases stated above.5 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 67a35that A does not belong to C, e. 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 67bparticular. For 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 67b5knowledge proper to the matter in hand or 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 67b10actual exercise, nor 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.

67b12But 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 A6 stand for the essence of good and B for the essence of bad, and again C for the essence of 67b15good. 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 d. For7 just as we saw that if B is true of all of which C is true, and8 A is true of all of which B is true, A is true of C, similarly with the word ‘think’. Similarly 67b20also with the word ‘is’; for we saw that if C is the same as L, and Bas A, C is the same as A. Similarly therefore with ‘opine’. Perhaps then this9 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, 67b25save incidentally. For it is possible to think this in many different ways. But we must consider this matter better.

Note del traduttore
  1. 1 Cf. i. 32 ff.
  2. 2 Read πρώτοις in l. 20 with A, B, C, and Waitz. σ΄ i.e. subject. ® i.e. attribute.
  3. 3 rr orhaps the text may stand.
  4. 4 δι.
  5. 5 66 20-6, 26-30.
  6. 6 That a man should think the same thing to be the essence of good and to be the essence of bad.
  7. 7 That the essence of good is the essence of bad.
  8. 8 The reference may be to 7762. I. 4.
  9. 9 All B is A AllCis 2B All C is B ᾿ Ὁ All Cis ἡ All A is C All A is C

Libro II, capitolo 22 On the Conversion of the Extremes in the first Figure.67b27–68b7

Inglese

67b27Whenever 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 and C belongs to everything to which A belongs, B is convertible 67b30with A, and B belongs to everything to which A belongs, through C as middle, and C is convertible with B through A as middle.1 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, C will 67b35be convertible with A. Suppose B does not belong to A; neither then will C: for ex hypothesis B belonged to all Ci And if C is convertible with B, B is convertible also with A:2 for C is said of that of all of which B is said3 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 68awhich B belongs: but C does not belong to that to which A belongs. And 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 68a5Cand D, and if 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 68a10what 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. But if A 68a15then C: for they are convertible. Therefore Cand D belong together. But this is impossible. When A belongs to the whole of B and to Cand 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 68a20is affirmed both 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, A will belong to all B.

68a25When, 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 68a30“A 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. 68a35But if D is preferable to A, then B must be less an object of aversion than C: for 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 hypothesis 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 68a40would prefer A, viz. 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 68bD) 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. To receive affection then is preferable in love to sexual intercourse. Love then is more dependent on friendship than on intercourse. And if it is most dependent 68b5on 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.

Note del traduttore
  1. 1 All A 15} All Bis A ον All Bis C No Bis A All Cis B All Cis B “. NoCisA No Ais B&B «. Nod is C
  2. 2 Read τῷ A τὸ B for τῷ A in l. 37 with Pacius. E No Lis A All Cis B ες NoCis 4 No Cis A All B is C
  3. 3 NosSisA “. Nod is B * Read ἀντιστρέφει {καὶ τὸ B), καὶ τὸ Β ἀντιστρέφει in l. 39. ὅ Read τὸ A, 76 Tin 1. 1 with Ay, Bo, Phil. and Pacius. c No &is A All Cis B All Bis C Ὁ NoCis A Nod is C οἷς Νὼὺ Α͂ 1528

Libro II, capitolo 23 Of Induction.68b8–37

Inglese

68b8It is clear then how the terms are related in conversion, and in respect of being in a higher degree objects of aversion 68b10or of desire.1 We must now state that not only 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.

68b15Now 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. For2 example let A stand for long-lived, B for bileless, and C 68b20for 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 proved3 that 68b25if 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.

68b30Such 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 proves 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.

Note del traduttore
  1. 1 Read φευκτότεροι ἢ (ἢ καὶ C) aiperorepo in l. 9 with A, B, C, and Waitz.
  2. 2 a21-25.
  3. 3 i.e, the subject of both predicates, which, being a particular thing, is of the nature of a minor term, and would be minor term in the first figure, though as subject of both premisses it actually serves as middle term in the supposed syllogism in the third figure. The transition from the syllogism in the third figure which yields only a particular conclusion to that in the first figure, which yields a universal conclusion, may be represented thus: All Cis A All C is A All Cis B All Bis C ον Some Bis A ον All Bis A

Citato nell'enciclopedia: DEDUZIONE · INDUZIONE · RAZIONALISMO · SILLOGISMO

Libro II, capitolo 24 Of Example.68b38–69a19

Inglese

68b38We 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 be known both that the middle1 belongs 68b40to the third term, and that the first belongs to that which resembles the third. For example let A be evil, B making 69awar 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 similar cases, e.g. that the war against 69a5the 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 D (for the 69a10war 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, 69a15but 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.

Note del traduttore
  1. 1 ch. 23.

Libro II, capitolo 25 Of Abduction.69a20–36

Inglese

69a20By 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. For1 in any of these cases it turns out that we approach more nearly to knowledge. For example let A stand for 69a25what can be taught, B 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 Cl' is equally or more probable than A C, we have a reduction: for we are nearer to knowledge, since we have taken a new term,”2 being so far without knowledge that A belongs to C Or again suppose that the terms intermediate between Zand 69a30C 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, 69a35and the intermediate terms are not few, I do not call this reduction: nor again when the statement BC is immediate: for such a statement is knowledge.

Note del traduttore
  1. 1 See note 26° 20.
  2. 2 viz. δ᾽, thus obtaining a certain premiss AB, and a premiss PC, on Ι 1 Read a comma before, not after, πάντων, l. 22. 1. no

Libro II, capitolo 26 Of Objection.69a37–70a2

Inglese

69a38An 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. 69bAn 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 arc brought in opposition to the premiss, and opposites can be 69b5proved only in the first and third figures. If 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 A stand for there being a single science, B for contraries. If a man premises that contraries are subjects of a single science, the 69b10objection 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.

69b15Similarly 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.

69b19In general if a man urges a universal objection he must 69b20frame 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.

69b24If 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 69b25will point out that 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 69b30to make objections. Consequently we bring objections in these figures only: for in them only are opposite syllogisms possible, since the second figure cannot produce an affirmative1 conclusion.

69b33Besides, an objection in the middle figure would require a fuller argument, e.g. if it2 should not be granted that d belongs to B, because C does not follow B.3 This can 69b35be made clear only by other premisses. But 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.”

69b39We must consider later the other kinds of objection, namely the objection from contraries, from similars, and from common 70aopinion, and inquire whether a particular objection cannot be elicited from the first figure or a negative objection from the second?

Note del traduttore
  1. 1 Read a comma before, not after, wavrwy, |, 22.
  2. 2 i.e. if the objection takes the form All A is Ὁ. No B is C. .. No Lis A.
  3. 3 It may be conjectured that this sentence is a gloss (so Susemihl), or that it should come after καταφατικῶς in l. 32. The fact that the second figure is necessarily negative is in effect the reason given in 70? 35-7 for the invalidity of proof by signs in that figure. 5. This sentence is inconsistent with what precedes, and 15 perhaps, as Cook Wilson has pointed out, a gloss added by some one who was familiar with the treatment of ἔνστασις in Δ᾽ οί, 1]. 25.

Libro II, capitolo 27 Of Likelihood, Sign, and Enthymeme.70a3–70b38

Inglese

70a3A probability and a sign are not identical, but a probability is a generally approved proposition: what men know to 70a5happen or not to happen, to be or not to be, for 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 70a10an 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 70a15milk is the middle term. Let 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 70a20former. The 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, but 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 is irrefutable if it is true (for 70a30it 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 70a35case: for 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.

70b1We must either divide signs in the way stated, and among them designate the middle term as the index1 (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 70b5proved through the first figure is most generally accepted and most true.

70b7It 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, 70b10this is not one of those affections which are natural to us; rather I refer to passions and desires when I speak of natural motions. 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 70b15individual kind, e.g. courage to lions, it is necessary that there should be a sign of it: for ex hypothesis 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, according to our usual 70b20manner 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 hypothesis 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, since it is necessary that it 70b25should 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. if a man 70b30is 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 if2 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, B for 70b35large 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 “: otherwise, there would not be a single sign correlative with each affection.

Note del traduttore
  1. 1 This points to the argument in the first figure, whose middle term is a genuine middle term.
  2. 2 Read τῷ for τῶν in l. 32 with codd. c, d, m, (τὸ C), and Waitz.

Citato nell'enciclopedia: SILLOGISMO

Latino di Boezio: Boethius, Migne, Patrologia Latina 64 (Paris 1847), coll. 639–712 (Corpus Corporum, University of Zurich). Public domain (1847). Digital text: Corpus Corporum.
Inglese (Oxford, 1928): A. J. Jenkinson, The Works of Aristotle translated into English, ed. W. D. Ross, vol. I (Oxford: Clarendon Press, 1928) (archive.org, University of Toronto scan). Public domain in the United States (published 1928) and in Canada (translator died 1928). Our transcription of the scan.
Inglese (Owen, 1853): Octavius Freire Owen, London: George Bell & Sons, 1889 (Bohn's Classical Library), vol. I, from the plates of the first edition (London: H. G. Bohn, 1853), same pagination (archive.org). Public domain. Our transcription of the scan.

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