(6) Whether all things are true by one truth, or by many?
(7) On the eternity of truth.
(8) On the unchangeableness of truth. _______________________
FIRST ARTICLE [I, Q. 16, Art. 1]
Whether Truth Resides Only in the Intellect?
Objection 1: It seems that truth does not reside only in the intellect, but rather in things. For Augustine (Soliloq. ii, 5) condemns this definition of truth, "That is true which is seen"; since it would follow that stones hidden in the bosom of the earth would not be true stones, as they are not seen. He also condemns the following, "That is true which is as it appears to the knower, who is willing and able to know," for hence it would follow that nothing would be true, unless someone could know it. Therefore he defines truth thus: "That is true which is." It seems, then, that truth resides in things, and not in the intellect.
Obj. 2: Further, whatever is true, is true by reason of truth. If, then, truth is only in the intellect, nothing will be true except in so far as it is understood. But this is the error of the ancient philosophers, who said that whatever seems to be true is so. Consequently mutual contradictories seem to be true as seen by different persons at the same time.
Obj. 3: Further, "that, on account of which a thing is so, is itself more so," as is evident from the Philosopher (Poster. i). But it is from the fact that a thing is or is not, that our thought or word is true or false, as the Philosopher teaches (Praedicam. iii). Therefore truth resides rather in things than in the intellect.
On the contrary, The Philosopher says (Metaph. vi), " The true and the false reside not in things, but in the intellect."
I answer that, As the good denotes that towards which the appetite tends, so the true denotes that towards which the intellect tends. Now there is this difference between the appetite and the intellect, or any knowledge whatsoever, that knowledge is according as the thing known is in the knower, whilst appetite is according as the desirer tends towards the thing desired. Thus the term of the appetite, namely good, is in the object desirable, and the term of the intellect, namely true, is in the intellect itself. Now as good exists in a thing so far as that thing is related to the appetite—and hence the aspect of goodness passes on from the desirable thing to the appetite, in so far as the appetite is called good if its object is good; so, since the true is in the intellect in so far as it is conformed to the object understood, the aspect of the true must needs pass from the intellect to the object understood, so that also the thing understood is said to be true in so far as it has some relation to the intellect. Now a thing understood may be in relation to an intellect either essentially or accidentally. It is related essentially to an intellect on which it depends as regards its essence; but accidentally to an intellect by which it is knowable; even as we may say that a house is related essentially to the intellect of the architect, but accidentally to the intellect upon which it does not depend.