Libro I, lezione XIIIDE VERITATE ET FALSITATE IN OPPOSITIS PROPOSITIONIBUS SINGULARIBUS DE FUTURO IN MATERIA CONTINGENTI

In his ergo et quae sunt et quae facta sunt necesse est affirmationem vel negationem veram vel falsam esse. In universalibus quidem universaliter, semper hanc quidem veram, illam vero falsam et in his quae sunt singularia, quemadmodum dictum est. In his vero, quae in universalibus non universaliter dicuntur, non est necesse. Dictum est autem et de his. In singularibus vero et futuris non similiter.

Nam si omnis affirmatio vel negatio vera vel falsa est, et omne necesse est vel esse vel non esse: quare si hic quidem dicat futurum aliquid, ille vero non dicat hoc idem ipsum, manifestum est quoniam necesse est verum dicere alterum ipsorum, si omnis affirmatio vel negatio vera vel falsa est. Utraque enim non erunt simul in talibus; nam si verum est dicere quoniam est album vel non album, necesse est esse album vel non album; et si est album vel non album, verum est affirmare vel negare; et si non est, mentitur; et si mentitur, non est. Quare necesse est, aut affirmationem aut negationem veram esse vel falsam. Nihil igitur neque est, neque fit, neque a casu, neque ad utrumlibet, nec erit, nec non erit; sed ex necessitate omnia et non utrumlibet: aut enim qui dicit verus est, aut qui negat; similiter enim vel fieret vel non fieret; utrumlibet enim nihil magis sic vel non sic se habet aut habebit.

Amplius, si est album nunc, verum erat dicere prius, quoniam erit album, quare semper verum fuit dicere quodlibet eorum, quae facta sunt, quoniam est vel erit. Quod si semper verum fuit dicere quoniam est vel erit, non potest hoc non esse vel non futurum esse; quod autem non potest non fieri, impossibile est non fieri, et quod impossibile est non fieri, necesse est fieri; omnia ergo, quae futura sunt, necesse est fieri. Nihil igitur utrumlibet, neque casu erit: nam si casu, non ex necessitate.

At vero neque quoniam neutrum verum est contingit dicere, ut quoniam neque erit neque non erit: primum enim cum sit affirmatio falsa, erit negatio non vera: et cum haec sit falsa, contingit affirmationem esse non veram.

Ad haec si verum est dicere, quoniam album est et magnum, oportet esse utrumque; si vero erit cras, oportet esse cras; si autem neque erit neque non erit cras, non erit utrumlibet, ut navale bellum: oportebit enim neque fieri navale bellum, neque non fieri.

La versione latina commentata da san Tommaso, nel testo dell'edizione leonina.

18a28In the case of that which is or which has taken place, propositions, whether positive or negative, must be true or false. Again, in the case of a pair of contradictories, either when the subject is universal and the propositions are of a 18a30universal character,¹ or when it is individual, as has been said,² one of the two must be true and the other false; whereas when the subject is universal, but the propositions are not of a universal character, there is no such necessity. We have discussed this type also in a previous chapter.³

18a33When the subject, however, is individual, and that which is predicated of it relates to the future, the case is altered.⁴ For⁵ if all propositions whether positive or negative! are 18a35either true or false, then any given predicate must either belong to the subject or not, so that if one man affirms that an event of a given character will take place and another denies it, it is plain that the statement of the one will correspond with reality and that of the other will not. For the predicate cannot both belong and not belong to the subject at one and the same time with regard to the future.

18b1Thus, if it is true to say that a thing is white, it must necessarily be white; if the reverse proposition is true, it will of necessity not be white. Again, if it is white, the proposition stating that it is white was true; if it is not white, the proposition to the opposite effect was true. And if it is not white, the man who states that it is is making a false statement; and if the man who states that it is white is making a false statement, it follows that it is not white. It may therefore be argued that it is necessary that affirmations or denials must be either true or false.

18b5Now if this be so, nothing is or takes place fortuitously, either in the present or in the future, and there are no real alternatives; everything takes place of necessity and is fixed. For either he that affirms that it will take place or he that denies this is in correspondence with fact, whereas if things did not take place of necessity, an event might just as easily not happen as happen; for the meaning of the word ‘fortuitous’ with regard to present or future events is that reality is so constituted that it may issue in either of two opposite directions.

18b10Again, if a thing is white now, it was true before to say that it would be white, so that of anything that has taken place it was always true to say ‘it is’ or ‘it will be’. But if it was always true to say that a thing is or will be, it is not possible that it should not be or not be about to be, and when a thing cannot not come to be, it is impossible that it should not come to be, and when it is impossible that it should not come to be, it must come to be. All, 18b15then, that is about to be must of necessity take place. It results from this that nothing is uncertain or fortuitous, for if it were fortuitous it would not be necessary.

18b17Again, to say that neither the affirmation nor the denial is true, maintaining, let us say, that an event neither will take place nor will not take place, is to take up a position impossible to defend. In the first place, though facts should. prove the one proposition false, the opposite would still be 18b20untrue.⁶ Secondly, if it was true to say that a thing was both white and large, both these qualities must necessarily belong to it; and if they will belong to it the next day,⁷ they must necessarily belong to it the next day.⁸ But if an event is neither to take place nor not to take place the next day, the element of chance will be eliminated.⁹ For example, it would be necessary that a sea-fight should neither 18b25take place nor fail to take place on the next day.

18b26These awkward results and others of the same kind follow, if it is an irrefragable law that of every pair of contradictory propositions, whether they have regard to universals and are stated as universally applicable, or whether they have regard to individuals, one must be true and the 18b30other false, and that there are no real alternatives, but that all that is or takes place is the outcome of necessity. There would be no need to deliberate or to take trouble, on the supposition that if we should adopt a certain course, a certain result would follow, while, if we did not, the result would not follow. For a man may predict an event ten thousand years beforehand, and another may predict the 18b35reverse; that which was truly predicted at the moment in the past will¹⁰ of necessity take place in the fullness of time.

I paragrafi del passo, nella traduzione di E. M. Edghill (The Works of Aristotle translated into English, ed. W. D. Ross, vol. I (Oxford: Clarendon Press, 1928)).

In those things which are, and have been,¹ the affirmation and negation must of necessity be true or false; in universals, as universals, always one true but the other false, and also in singulars, as we have shown; but in the case of universals not universally enunciated, there is no such necessity, and concerning these we have also spoken, but as to singulars and futures, this is not the case. For if every affirmation or negation be true or false, it is also necessary that every thing should exist or should not exist, for if one man says that a thing will be, but another denies the same, one of them must evidently of necessity speak truth, if every affirmation or negation be true or false, for both will not subsist in such things at one and the same time. Thus if it is true to say that “a thing is white,” or that “it is not white,” it must of necessity be “white” or not “white,” and if it is white or not white, it was true to affirm or to deny it: also if it is not, it is falsely said to be, and if it is falsely said to be, it is not; so that it is necessary that either the affirmation or the negation should be true or false. Indeed there is nothing which either is, or is generated fortuitously, nor casually, nor will be, or not be, but all things are from necessity, and not casually, for either he who affirms speaks truth, or he who denies, for in like manner it might either have been or not have been, for that which subsists casually neither does nor will subsist more in this way than in that.² Moreover if a thing is now “white,” it was true to say before that it will be “white,” so that it was always true to say of any thing generated that it either is, or that it will be; but if it was always true to say that it is, or will be, it is impossible that this is not, nor should be; and whatever must of necessity be, it is impossible that it should not have been generated, and what it is impossible should not have been generated must of necessity have been generated; wherefore all things that will be, it is necessary should be generated, and hence there will be nothing casual nor fortuitous, for if it were fortuitous it would not be of necessity. Nor is it possible to say, that neither of them is true, as that it will neither be, nor will not be, for in the first place the affirmation being false, the negation will not be true, and this being false, it results that the affirmation is not true. And besides, if it were true to say that a thing is at the same time “white” and “great,” both must of necessity be, but if it shall be to-morrow, it must necessarily be to-morrow, and if it will neither be nor will not be to-morrow, it will not be a casual thing, for example, a naval engagement, for it would be requisite that the engagement should neither occur nor not occur.

These and similar absurdities then will happen, if of every affirmation and negation, whether in respect of universals enunciated universally, or of singulars, it is necessary that one of the opposites be true and the other false, but that nothing happens casually in those things which subsist, but that all are, and are generated of necessity; so that it will neither be necessary to deliberate nor to trouble ourselves, as if we shall do this thing, something definite will occur, but if we do not, it will not occur. For there is nothing to prevent a person for ten thousand years asserting that this will happen, and another person denying it, so that of necessity it will have been then true to assert either of them. And it makes no difference whether any persons have uttered a contradiction or not, for

Aristotle traces here the institution of a word to the primary concept of the thing, so that if affirmation is true, a thing is, if negation is true, a thing is not. If either be true or false, he who affirms or denies says truly or falsely, so that if affirmative be true or false, a thing must necessarily exist or not exist. He alleges two enthymematic proofs, terminating in a reductio ad absu·dum. it is evident that the things are so, although the one should not have affirmed any thing, or the other have denied it, since it is not, because it has been affirmed or denied, that therefore a thing will or will not be, neither will it be more so for ten thousand years than for any time whatever. Hence if a thing so subsisted in every time that one of these is truly asserted of it, it was necessary that this should take place; and each thing generated, always so subsisted, as to have been generated from necessity, for when any one truly said that it will be, it was not possible not to have been generated, and of that which is generated, it was always true to say that it will be.

But³ if these things are impossible—(for we see that there is a beginning of future things, both from our deliberation and practice, and briefly in things which do not always energize, there is equally a power of being and of not being, in which both to be and not to be occurs, as well as to have been generated and not to have been generated; and, indeed, we have many things which evidently subsist in this manner, for example, it is possible for this garment to have been cut in pieces, and it may not be cut in pieces, but be worn out beforehand, so also it is possible that it may not be cut in pieces, for it would not have been worn out before, unless it had been possible that it might not be cut in pieces, and so also in respect of other productions, which are spoken of according to a power of this kind—) then it is evident that all things neither are, nor are generated of necessity, but that some things subsist casually, and that their affirmation is not more true than their negation, and that there are others in which one of these subsists more frequently, and for the most part,⁴ yet so, that either might possibly have occurred, but the other not.⁵

Wherefore, being, must of necessity be when it is,⁶ and non-being, not be, when it is not; but it is not necessary that every being should be, nor that non-being should not be, since it is not the same thing for every being to be from necessity, when it is, and simply to be from necessity, and in like manner as to non-being. There is the same reasoning also in the case of contradiction; to be or not to be is necessary for every thing, also that it shall, or shall not be, yet it is not requisite to speak of each separately, but I say, for instance, that it is necessary for a naval action to occur or not occur to-morrow, yet it is not necessary that there should be a naval action to-morrow, nor that there should not be; it is necessary, however, that it should either be or not be. Wherefore, since assertions and things are similarly true, it is evident that things which so subsist, as that whatever have happened, the contraries also were possible, it is necessary that contradiction should subsist in the same manner, which happens to those things which are not always, or which not always, are not. For of these, one part of the contradiction must necessarily be true or false, not indeed this or that, but just as it may happen, and one must be the rather true, yet not already true nor false;⁷ so that it is evidently not necessary that of every affirmation and negation of opposites, one should be true, but the other false;⁸ for it does not happen in the same manner with things which are not, but which either may or may not be, as with things which are, but it happens as we have said⁹ Compare the philosophical principle of formal necessity in this chapter with Bp. Butler’s distinction between, “by necessity,” and acting “necessarily,” Analogy, ch. 6, also his Introduction, and part ii. ch. 2, upon the nature of the contingent and proof.

I capitoli interi, nella traduzione di 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).