Libro II, lezione XIAN AD ILLUD QUOD EST, NECESSARIUM ESSE, SEQUATUR ID QUOD EST, POSSIBILE ESSE?

Dubitabit autem aliquis, si ad illud quod est, necessarium esse, illud quod est, possibile esse, sequatur. Nam si non sequatur, contradictio sequetur, quae est, non possibile esse: et si quis hanc non dicat esse contradictionem, necesse est dicere, possibile non esse: quae utraeque falsae sunt de necesse esse.

At vero rursus idem videtur esse possibile aliquid incidi et non incidi, et esse et non esse: quare erit necesse esse, contingens non esse. Hoc autem falsum est.

Manifestum est autem quod non omne possibile, vel esse, vel ambulare, etiam opposita potest; sed est in quibus non sit verum. Primum quidem in his quae non secundum rationem possunt; ut ignis calefactibilis est, et habet vim irrationalem. Quae igitur secundum rationem potestates sunt, eaedem plurium etiam contrariorum sunt. Irrationales vero non omnes: sed (quemadmodum dictum est) ignem non esse possibile calefacere et non; neque quaecunque alia semper agunt. Alia vero possunt, et secundum irrationales potestates simul opposita suscipere. Sed hoc huius gratia: dictum est, quoniam non omnis potestas oppositorum susceptiva est, neque quaecunque secundum eamdem speciem dicuntur.

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

22b29It may be questioned whether the proposition ‘it may be’ follows from the proposition ‘it is necessary that it should 22b30be’. If not, the contradictory must follow, namely that it cannot be. or, if a man should maintain that this is not the contradictory, then the proposition ‘it may not be’.

22b32Now both of these are false of that which necessarily is. At the same time, it is thought that if a thing may be cut it may also not be cut, if a thing may be it may also not be, and thus it would follow that a thing which must 22b35necessarily be may possibly not be; which is false. It is evident, then, that it is not always the case that that which may be or may walk possesses also a potentiality in the other direction. There are exceptions. In the first place we must except those things which possess a potentiality not in accordance with a rational principle, as fire possesses the potentiality of giving out heat, that is, an irrational capacity. Those potentialities which involve a rational principle are potentialities of more than one result, 23athat is, of contrary results; those that are irrational are not always thus constituted. As I have said, fire cannot both heat and not heat, neither has anything that is always actual any twofold potentiality. Yet some³ even of those potentialities which are irrational admit of opposite results, 23a5However, thus much has been said to emphasize the truth that it is not every potentiality which admits of opposite results, even where the word is used always in the same sense.

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)).

The consequences are rightly placed thus: “it happens to be,” follows, “it is possible to be,” and this reciprocates with that; also, “it is not impossible to be” and “it is not necessary to be.” But, “it is not necessary not to be,” and, “it¹ is not impossible not to be;” follow, “it is possible not to be,” and, “it may happen not to be;” and, “it is necessary not to be,” and, “it is impossible to be,” follow, “it is not possible to be,” and, “it does not happen to be;” but, “it is necessary to be,” and also, “it is impossible not to be,” follow, “it is not possible not to be,” and, “it is not contingent not to be:” what we say however may be seen from the following description:

It is not impossible to be It is not necessary to be. 2 It is possible not to be It may happen not to be It is not impossible not to be It is not necessary not to be.

It is impossible to be It is necessary not to be. 4 It is not possible not to be It may happen not to be It is impossible not to be It is necessary to be.

Therefore the impossible, and the not impossi-ble, follow contradictorily the contingent, and the possible, and the non-contingent, and the not possible, and vice versâ; * for the negation of the impossible, namely, “ it is not impossible to be,” follows, “ it is possible to be,” but affirmation follows negation, for, “ it is im-possible to be ” follows “ it is not possible to be,” since “ it is impossible to be,” is affirmation, but, “ it is not impossible to be,” is negation.

Let us next see how it is with necessary matter, now it is evident that it does not subsist thus, but contraries follow, and contradictories (are placed) separately,² for, “ it is not ne-cessary to be,” is not the negation of “ it is ne-cessary not to be,” since both, may possibly be true of the same thing, as that which necessarily, is not, need not of necessity, be. But the reason why the necessary follows not, in like manner, other propositions, is that the impossible being enunciated contrarily to the ne-cessary, signifies the same thing; for what it is impossible should exist, must not of necessity be, but not be, and what is impossible should not be, this must of necessity be; so that if these similarly follow the possible and the not possible, these (do so) in a contrary mode,³ since the necessary and the impossible do not signify the same thing, but, as we have said, vice versâ. Or is it impossible that the contradictories of the necessary should be thus disposed? for, what, “is necessary to be” is “possible to be,” since if not, negation would follow, as it is necessary either to affirm or deny, so that, if it is not possible to be, it is impossible to be, wherefore it would be impossible for that to be, which necessarily is, which is absurd, but the enunciation, “it is not impossible to be” follows the other, “it is possible to be,” which again is followed by, “it is not necessary to be,” whence it happens that what necessarily exists does not necessarily exist, which is absurd. But again neither does, “it is necessary to be” follow “it is possible to be,” nor does the proposition, “it is necessary not to be,” for to that, both, may occur, but whichever of these is true,⁴ those⁵ will be no longer true, for at one and the same time, it is possible to be, and not to be, but if it is necessary either to be or not to be, both, will not be possible. It remains therefore, that “it is not necessary not to be,” follows “it is possible to be;” for this⁶ is also true in respect of what is necessary to be, since this becomes the contradiction of that proposition which follows, viz. “it is not possible to be;” as “it is impossible to be,” and “it is necessary not to be,” follow that, of which the negation is, “it is not necessary not to be.” Wherefore these contradictions follow according to the above-mentioned mode, and nothing absurd results, when they are thus disposed.⁷ Still it may be doubted whether “it is possible to be,” follows “it is necessary to be,” for if it does not follow, the contradiction will be consequent, namely, “it is not possible to be,” and if a man should deny this to be a contradiction, it will be necessary to call, “it is possible not to be,” a contradiction, both which are false in respect of necessary matter. Nay, on the contrary, it appears to be possible that the same thing should “be cut” and “not be cut,” should “be” and “not be,” so that what necessarily “is,” may happen “not to be,” which is false. Nevertheless it is evident that not every thing which can “be,” and can “walk,” is capable also of the opposites, for in some cases this is not true. In the first place, in those things which are potent irrationally,⁸ as fire is calorific, and has irrational power; rational powers then are those of many things, and of the contraries; but not all irrational powers, for, as we have said, fire cannot heat, and not heat, nor such other things as always energize. Yet even some irrational powers can at the same time receive opposites; but this has been stated by us, because not every power is susceptible of contraries, not even such as are predicated, according to the same species. Moreover, some powers are equivocal, for the possible is not predicated, simply; but one thing is (called so), because it is true, as being in an energy, as it is possible for a man to walk, because he walks, and in short, a thing is possible to be, because that is already in energy which is said to be possible; on the other hand, another thing (is said to be possible), because it may be in energy; as it is possible to walk, because a man may walk. Now this power exists in movable natures only, but that in immovable; but with respect to both, it is true to say, that it is not impossible to walk or to be, and that a man is now walking and energizing, and has the power to walk, hence it is not true⁹ to predicate that which is thus possible, in respect of necessary matter, simply, but the other is true. Wherefore since the universal follows the particular, to be able to be, but not all ability, follows that which is of necessity, and indeed the necessary and the non-necessary may perhaps be the principle of the existence, or of the non-exist-ence of all things, and we should consider other things as consequent upon these.¹⁰ Hence from what we have stated, it is clear that whatever exists of necessity, is in energy, so that if eternal natures are prior in existence, energy also is prior to power, and some things, as the first substances, are energies without power, but others with power, namely, those which are prior by nature, but posterior in time: lastly, there are some which are never energies, but are capacities only.

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).