Authors/Thomas Aquinas/posteriorum/L1/Lect14

Lecture 14 Demonstration bears upon and proceeds from things which are per se

Latin	English
	Lecture 14 (75al8-37) DEMONSTRATION BEARS UPON AND PROCEEDS FROM THINGS WHICH ARE PER SE
lib. 1 l. 14 n. 1 Postquam ostendit philosophus quod demonstratio est de necessariis et ex necessariis, consequenter ostendit quod est de his, quae sunt per se et ex his, quae sunt per se. Et circa hoc tria facit: primo, ostendit quod demonstratio est de his, quae sunt per se, idest quod conclusiones demonstrationis sunt per se; secundo, movet dubitationem et solvit; ibi: et tamen opponet etc.; tertio, ostendit quod demonstratio est ex his, quae sunt per se, idest quod principia demonstrationis oportet per se esse; ibi: quoniam autem ex necessitate et cetera.	After showing that demonstration proceeds from necessary things, the Philosopher then shows that it is concerned with things that are per se and proceeds from things that are per se. In regard to this he does three things. First, he shows that demonstration is concerned with things that are per se, i.e., that the conclusions of demonstrations are per se. Secondly, he raises a problem (75a21). Thirdly, he shows that demonstration proceeds from things that are per se, i.e., that the principles of demonstrations must be per se (75a28).
lib. 1 l. 14 n. 2 Dicit igitur primo quod demonstrativa scientia non potest esse accidentium, quae non sunt per se, sicut determinatum est per se superius, scilicet quod accidens per se est in cuius definitione ponitur subiectum; sicut par aut impar est per se accidens numeri. Album autem animalis non est per se accidens: quia animal non ponitur in eius definitione.	He says therefore first (75a18) that demonstrative science cannot bear on accidents that are not per se in the way that per se was explained above, namely, that a per se accident is one in whose definition the subject is mentioned, as “even” or “odd” is a per se accident of number. But “white” is not a per se accident of animal, because animal is not mentioned in its definition.
Quod autem de huiusmodi accidentibus, quae non sunt per se, non possit esse demonstratio, sic probat. Accidens, quod non est per se, contingit non inesse (de hoc enim accidente loquimur); si ergo demonstratio fieret de accidente, quod non est per se, sequeretur quod conclusio demonstrationis non esset necessaria: cuius contrarium supra ostensum est.	That there cannot be demonstration bearing on accidents that are not per se he proves in the following way: An accident which is not per se might happen not to be present (and this is the accident under discussion). Therefore, if a demonstration were to bear on an accident which is not per se, it would follow that the conclusion of the demonstration would not be necessary: which is contrary to what has been established.
Quod autem accidens, quod non est per se, non necessario insit, ex hoc potest haberi. Si enim aliquod accidens ex necessitate et semper insit subiecto, oportet quod causam habeat in subiecto, qua posita, non possit accidens non inesse. Quod quidem contingit dupliciter. Uno modo, quando ex principiis speciei accidens causatur; et tale accidens dicitur per se passio vel proprium. Alio modo quando accidens causatur ex principiis individui; et hoc est accidens inseparabile. Omne autem accidens, quod causatur ex principiis subiecti, si debeat definiri, oportet quod subiectum ponatur in sua definitione: nam unumquodque definitur ex propriis principiis; et sic oportet omne accidens, quod ex necessitate inest subiecto, esse accidens per se. Illa ergo quae non sunt per se, non ex necessitate insunt.	That an accident which is not per se does not inhere necessarily can be obtained from the following: If an accident inheres necessarily and always in a subject, it must have its cause in the subject—in which case the accident cannot but inhere. Now this can occur in two ways: in one way, when it is caused from the principles of the species, and such an accident is called a per se attribute or property; in another way, when it is caused from the principles of the individual, and this is called an inseparable accident. In either case every accident which is caused from the principles of the subject must, if it is defined, be defined in such a way as to mention the subject in its definition: for a thing is defined in terms of its proper principles. Thus it is clear that an accident which necessarily inheres in its subject must be a per se accident. Therefore, those that are not per se do not inhere of necessity.
lib. 1 l. 14 n. 3 Videtur autem quod Aristoteles utatur demonstratione circulari, quam supra improbavit. Ostenderat enim supra quod demonstratio necessariorum est ex hoc quod est eorum quae sunt per se; nunc autem e converso ostendit quod demonstratio est eorum quae sunt per se, quia est necessariorum. Sed dicendum quod supra Aristoteles non solum ostendit demonstrationem esse necessariorum propter hoc, quod est eorum quae sunt per se, sed ex definitione eius quod est scire; et hic fuit verus demonstrationis modus. Quod autem ostendit demonstrationem esse necessariorum propter hoc, quod est eorum quae sunt per se, non est vera demonstratio, sed est ostensio ad hominem, apud quem notum est quod demonstratio sit eorum quae sunt per se.	It seems, however, that Aristotle is using the circular demonstration, which he previously repudiated. For he had proved earlier that a demonstration is concerned with necessary things, because it is concerned with, things which are per se; but now he shows that demonstration is con-: 1, cerned with things which are per se, because it is concerned with things which are necessary. The answer is that above Aristotle proved that demonstration is concerned with necessary things not only because it is concerned with things which are per se but also because of the definition of scientific knowing—and this was a true way to demonstrate. But the proof that demonstration is concerned with necessary things because it is concerned with things which are per se, is not a demonstration but an indication directed to a person who already knows that demonstration is concerned with things which are per se.
lib. 1 l. 14 n. 4 Deinde cum dicit: et tamen opponet etc., movet dubitationem quamdam. Et circa hoc duo facit. Primo, ponit dubitationem dicens quod potest aliquis forte opponere: si conclusio, quae sequitur ex contingentibus vel ex his quae sunt per accidens, non est necessaria; quare de contingentibus fit interrogatio sive de his quae sunt per accidens, ut ex iis datis procedatur ad conclusionem, cum tamen in syllogismo requiratur quod conclusio ex necessitate accidat. Et quod interrogatio fiat de contingentibus vel ex his, quae sunt per accidens, manifestat per hoc quod subdit: nihil enim differt, si aliquis interrogatus contingentia, postea dicat conclusionem. Quasi dicat: ita potest inferri conclusio ex contingentibus interrogatis et concessis, sicut ex necessariis: utrisque enim eadem forma syllogizandi est.	Then (75a21) he raises a problem in regard to which he does two things. First, he states the problem, saying that someone may perhaps, object that if the conclusion which follows from contingent things or things which are per accidens is not necessary, why are inquiries made concerning contingent things or things which are per accidens, so that from such data one may reach a conclusion, since it is required of the’ syllogism that the conclusion follow of necessity. That inquiries touching contingent things or things which are per accidens do occur is evident from his next statement, namely, that it makes no difference whether one inquires into contingent things and then gives his conclusion. As if to say: A conclusion can be drawn from contingent things that have been investigated and verified, just as from necessary things. For each employs the same syllogistic form.
lib. 1 l. 14 n. 5 Secundo; ibi: oportet autem etc., solvit dicens quod non ita interrogatur de praemissis contingentibus, quasi conclusio sit necessaria absolute propter interrogata, idest propter praemissa contingentia; sed quia necesse est dicenti praemissa conclusionem dicere, et dicere vera in conclusione, si vera sunt, quae praemissa sunt: quasi dicat quod licet ex praemissis contingentibus non sequatur conclusio necessaria necessitate absoluta, sequitur tamen secundum quod est ibi necessitas consequentiae, secundum quod conclusio sequitur ex praemissis.	Secondly (75a24), he solves the difficulty and says that questions solved by contingent premises are not of such a nature that the conclusion is necessary absolutely, on the basis of the things investigated, i.e., in virtue of the contingent premises, but because it is necessary for the one who admits the premises to admit the conclusion and to admit truth in the conclusion, if the things premised are true. It is as though he were saying that although a conclusion which is necessary with absolute necessity does not follow from contingent premises, yet it follows with the necessity of consequence according to which the conclusion follows from premises.
lib. 1 l. 14 n. 6 Deinde cum dicit: quoniam autem etc., ostendit quod demonstratio sit ex his, quae sunt per se, tali ratione. Demonstratio est ex necessariis et de necessariis. Et hoc ideo, quia est scientifica, idest faciens scire. Ea autem, quae non sunt per se, non sunt necessaria: sunt enim per accidens et huiusmodi non sunt necessaria, ut dictum est. Sed illa sunt ex necessitate circa unumquodque genus, quaecunque sunt per se et conveniunt unicuique secundum quod unumquodque est. Relinquitur ergo quod demonstratio non possit esse nisi ex his, quae sunt per se et de talibus.	Then (75a28) he shows that demonstration proceeds from things which are per se, using the following argument: Demonstration proceeds from necessary things and bears on necessary things—and this because it is scientific, i.e., makes one know scientifically. But things which are not per se are not necessary, for they are per accidens and, being such, are not necessary, as has been stated above. On the other hand, those things bear with necessity on a genus which are per se and belong to it according to what it is. It follows, therefore, that demonstration cannot be from anything or of anything but what is per se.
lib. 1 l. 14 n. 7 Ulterius autem ostendit quod etiam si praemissa essent semper, et necessaria, et vera, et non per se, non tamen sciretur de conclusione propter quid; sicut patet in syllogismis, qui fiunt per signa, in quibus conclusionem, quae est per se, non scit aliquis per se, neque propter quid. Sicut si aliquis probaret quod omne elementum est corruptibile, per hoc quod videtur tempore antiquari, esset quidem probatio per signum, non autem per se, neque propter quid: quia propter quid scire est per causam scire. Oportet ergo medium esse causam eius, quod in demonstratione concluditur. Et hoc manifestum est ex praemissis: quia oportet et medium inesse tertio propter ipsum, idest per se, et similiter primum medio. Primum autem et tertium vocat duas extremitates.	He further shows that even if the premises were always both necessary and true but not per se, one would not know the cause why [propter quid] of the conclusion. This is clear in syllogisms which prove through signs, for although the conclusion be per se, one does not know it per se nor propter quid. For example, if someone were to prove that every element corruptible on the ground that it is seen to grow old. This would be a proof through a sign but neither per se nor propter quid, because to know propter quid one must know through the cause. Therefore, the middle must be the cause of that which is concluded in the demonstration. And this is obvious from the premises: for the middle must inhere in the third causatively, i.e., per se, and likewise the first in the middle. Here he calls the two extremes the first and the third.