Commentaria in Primam Partem Summae Theologiae

In the title, "contrary" is taken properly, as contrariety is distinguished from the other species of opposition.

In the body, one conclusion, answering the question affirmatively: The true and the false are contraries. – It is proved thus. The false is to say or to seem that being is not, or that non-being is: therefore the false signifies an inadequate apprehension of the thing: therefore the false posits something, and determines a subject for itself: therefore it is opposed to the true neither contradictorily nor privatively, but contrarily.

The antecedent is proved from Metaphysics IV, text 27. The first consequence is evident, and it is confirmed by the meaning of the true, namely because it posits an adequate apprehension of the thing. The second, however, is evident in itself: because a disformed apprehension is something. The last, however, is proved from the difference between opposites that are contradictory, privative, and contrary: namely, because in the first, one is a pure negation without a subject; in the second, a negation in a subject; in the third, a position in a subject.

II. Note here that the text presupposes that true and false are opposed, as if this were self-evident; and it seeks only to determine the mode of opposition. And therefore the third consequence suffers no calumny. – The confirmation of the first consequence from the signification of the true is also most effective, if what is believed at Metaphysics IV ¹ is credited: for there no disparity with respect to signifying something positive is posited, and yet each is defined. For the true, says Aristotle, is being's esse, and non-being's non-esse: but the false is being's non-esse, and non-being's esse. Hence by the same reason by which the true signifies something positive, namely an enunciation conformable to being and non-being, so too the false signifies an enunciation disconformable to both; and it does not signify a negation of conformity, as those cited in the text supposed.

III. Concerning the first consequence, namely, that the false posits an inadequate apprehension of the thing ², note that it can be understood in two ways. In one way, that "false" would signify formally a disformed apprehension, as "black" signifies a collective color. In the other way, that it posits the relation of disformity formally, and the apprehension fundamentally; just as "unlike" signifies a relation, and posits a quality. It cannot be understood in the first way: for it would follow that one of two contraries, taken formally, would pass over into the other: which is unintelligible. For it cannot be perceived that whiteness becomes blackness, but rather that the thing which is white is changed into black. The consequence is evident from the Categories ³, where it is said that one and the same sentence is received as true and false. For if one and the same statement is at one time true and at another time false, and the statement formally signifies both the true and the false, then one of two contraries must formally receive the other. Hence from the very fact that one and the same sentence is at one time true and at another false, it is evident that the true and the false signify something in the sentence, and not the statement itself. In sign of this, since it should have been subjoined in the text that the false signifies something positive in a determinate subject, nothing else was subjoined except that the false posits an inadequate apprehension, so that you would understand that inadequacy is signified in the apprehension.

IV. There is, however, a point to be noted here: just as the like and the unlike are opposed as contraries, and they can be contrary to each other in two ways—namely in respect of the foundation, as when something white, which was like another white thing, changes into black, which is unlike the white; and in respect of the terminus, namely if the terminus were changed into black—so truth is indeed opposed as a contrary to falsehood, and this can happen in two ways. On the side of the terminus, when one and the same statement becomes false from being true on account of a change in the thing signified; as is clear in contingent matter. On the side of the foundation, however, when the foundations themselves are contraries. Now the foundation of truth and falsity, as is clear from what has been said ⁴, is an enunciation, or the intellect's acceptance of one. And among enunciations, as is proved in Book II of the Perihermeneias ⁵, contrariety is found first between the affirmative and the negative of the same predicate affirmed of the same subject, etc., one of which must be true and the other false. Therefore, from first to last, the intellect is changed from truth into falsity on the side of the foundation when it passes from the enunciation of one part of a contradiction to the other. But since the change on the side of the terminus in truth and falsity either is not a genuine contrariety (because the statement passes from one to the other without any change in itself); or if it is taken as a true contrariety, such as can exist among relatives, it does not have the character of contrariety from the change of the terminus (since the change of the terminus occurs both from contrary to contrary and from affirmation to negation, or conversely), whereas the change from truth into falsity on the side of the foundation does have the character of contrariety from the change between the foundations (because, namely, the change of the intellect from an affirmative opinion to a negative one, or conversely, is truly between contraries); and what is more, from the contrariety of the foundations there arises the contrariety of truth and falsity according to the terminus (for this is why the statement "Socrates is sitting", when he rises, is said to take on the other contrary, namely falsity, because it is contrary to that which is true, namely "Socrates is not sitting"; for unless there were a contrariety between the statements themselves, the change from truth into falsity would not have the character of true contrariety)—therefore the text makes mention only of the contrariety arising on the side of the foundation. And deservedly so: because we see that the nature of a relation follows most closely the nature of its foundation, since it is either identical with it or, as it were, a natural passion of it.

V. In response to the second, note that he there uses the term contrariety broadly, insofar as it also includes privative opposition; as is clear from good and evil taken transcendentally, and from the words added below, namely, just as every privation is founded in a subject, so every evil etc. The Author did this not out of carelessness, but because, as far as the force of the argument goes, the judgment is the same for contraries and for privatively opposed things, he wished to intimate that the proper response ought also to be the same, whether things are opposed contrarily or privatively. And for this reason he taught that the name of contrariety should be extended.