29 R. Is Truth then so called for any other reason than as being that by which everything is true which is true? A. For no other reason. R. Is it rightly called true for any ground than that it is not false? A. To doubt this were madness. R. Is that not false which is accommodated to the similitude of anything, yet is not that the likeness of which it appears? A. Nothing indeed do I see which I would more willingly call false. But yet that is commonly called false, which is far removed from the similitude of the true. R. Who denies it? But yet because it implies some imitation of the true. A. How? For when it is said, that Medea flew away with winged snakes harnessed to her car, that thing on no side imitates truth; inasmuch as the thing is naught, nor can that thing imitate anything, when itself is absolutely nothing. R. You say right; but you do not note that that thing which is absolutely nothing, cannot even be called false. For if it is false, it is: if it is not, it is not false. A. Shall we not then say that monstrous story of Medea is false? R. Assuredly not; for if it is false, how is it a monstrous story? A. Admirable! Then when I say
“The mighty winged snakes I fasten to my car,”
do I not say false? R. You do, assuredly: for that is which you say to be false. A. What, I pray? R. That sentence, forsooth, which is contained in the verse itself. A. And pray what imitation of truth has that? R. Because it would bear the same tenor, even if Medea had truly done that thing. Therefore in its very terms a false sentence imitates true sentences. Which, if it is not believed, in this alone does it imitate true ones, that it is expressed as they, and it is only false, it is not also misleading. But if it obtains faith, it imitates also those sentences which, being true, are believed true. A. Now I perceive that there is a great difference between those things which we say and those things concerning which we say anything; wherefore I now assent: for this proposition alone held me back, that whatever we call false is not rightly so called, unless it have an imitation of something true. For who, calling a stone false silver, would not be justly derided? Yet if any one should declare a stone to be silver, we say that he speaks falsely, that is, that he utters a false sentence. But it is not, I think, unreasonable that we should call tin or lead false silver, because the thing itself, as it were, imitates that: nor is our sentence declaring this therefore false, but that very thing concerning which it is pronounced.
Source: Soliloquies (New Advent)