Summa Theologica, by St. Thomas Aquinas, [1947], at sacred-texts.com
We next consider falsity. About this four points of inquiry arise:
(1) Whether falsity exists in things?
(2) Whether it exists in the sense?
(3) Whether it exists in the intellect?
(4) Concerning the opposition of the true and the false.
Objection 1: It appears that falsity does not exist in things. For Augustine says (Soliloq. ii, 8), "If the true is that which is, it will be concluded that the false exists nowhere; whatever reason may appear to the contrary."
Objection 2: Further, false is derived from "fallere" [to deceive]. But things do not deceive; for, as Augustine says (De Vera Relig. 33), they show nothing but their own species. Therefore the false is not found in things.
Objection 3: Further, the true is said to exist in things by conformity to the divine intellect, as stated above (Q[16]). But everything, in so far as it exists, imitates God. Therefore everything is true without admixture of falsity; and thus nothing is false.
On the contrary, Augustine says (De Vera Relig. 34): "Every body is a true body and a false unity: for it imitates unity without being unity." But everything imitates the divine unity yet falls short of it. Therefore in all things falsity exists.
I answer that, Since true and false are opposed, and since opposites stand in relation to the same thing, we must needs seek falsity, where primarily we find truth; that is to say, in the intellect. Now, in things, neither truth nor falsity exists, except in relation to the intellect. And since every thing is denominated simply by what belongs to it "per se," but is denominated relatively by what belongs to it accidentally; a thing indeed may be called false simply when compared with the intellect on which it depends, and to which it is compared "per se" but may be called false relatively as directed to another intellect, to which it is compared accidentally. Now natural things depend on the divine intellect, as artificial things on the human. Wherefore artificial things are said to be false simply and in themselves, in so far as they fall short of the form of the art; whence a craftsman is said to produce a false work, if it falls short of the proper operation of his art.
In things that depend on God, falseness cannot be found, in so far as they are compared with the divine intellect; since whatever takes place in things proceeds from the ordinance of that intellect, unless perhaps in the case of voluntary agents only, who have it in their power to withdraw themselves from what is so ordained; wherein consists the evil of sin. Thus sins themselves are called untruths and lies in the Scriptures, according to the words of the text, "Why do you love vanity, and seek after lying?" (Ps. 4:3): as on the other hand virtuous deeds are called the "truth of life" as being obedient to the order of the divine intellect. Thus it is said, "He that doth truth, cometh to the light" (Jn. 3:21).
But in relation to our intellect, natural things which are compared thereto accidentally, can be called false; not simply, but relatively; and that in two ways. In one way according to the thing signified, and thus a thing is said to be false as being signified or represented by word or thought that is false. In this respect anything can be said to be false as regards any quality not possessed by it; as if we should say that a diameter is a false commensurable thing, as the Philosopher says (Metaph. v, 34). So, too, Augustine says (Soliloq. ii, 10): "The true tragedian is a false Hector": even as, on the contrary, anything can be called true, in regard to that which is becoming to it. In another way a thing can be called false, by way of cause---and thus a thing is said to be false that naturally begets a false opinion. And whereas it is innate in us to judge things by external appearances, since our knowledge takes its rise from sense, which principally and naturally deals with external accidents, therefore those external accidents, which resemble things other than themselves, are said to be false with respect to those things; thus gall is falsely honey; and tin, false gold. Regarding this, Augustine says (Soliloq. ii, 6): "We call those things false that appear to our apprehension like the true:" and the Philosopher says (Metaph. v, 34): "Things are called false that are naturally apt to appear such as they are not, or what they are not." In this way a man is called false as delighting in false opinions or words, and not because he can invent them; for in this way many wise and learned persons might be called false, as stated in Metaph. v, 34.
Reply to Objection 1: A thing compared with the intellect is said to be true in respect to what it is; and false in respect to what it is not. Hence, "The true tragedian is a false Hector," as stated in Soliloq. ii, 6. As, therefore, in things that are is found a certain non-being, so in things that are is found a degree of falseness.
Reply to Objection 2: Things do not deceive by their own nature, but by accident. For they give occasion to falsity, by the likeness they bear to things which they actually are not.
Reply to Objection 3: Things are said to be false, not as compared with the divine intellect, in which case they would be false simply, but as compared with our intellect; and thus they are false only relatively.
To the argument which is urged on the contrary, likeness or defective representation does not involve the idea of falsity except in so far as it gives occasion to false opinion. Hence a thing is not always said to be false, because it resembles another thing; but only when the resemblance is such as naturally to produce a false opinion, not in any one case, but in the majority of instances.
Objection 1: It seems that falsity is not in the senses. For Augustine says (De Vera Relig. 33): "If all the bodily senses report as they are affected, I do not know what more we can require from them." Thus it seems that we are not deceived by the senses; and therefore that falsity is not in them.
Objection 2: Further, the Philosopher says (Metaph. iv, 24) that falsity is not proper to the senses, but to the imagination.
Objection 3: Further, in non-complex things there is neither true nor false, but in complex things only. But affirmation and negation do not belong to the senses. Therefore in the senses there is no falsity.
On the contrary, Augustine says (Soliloq. ii, 6), "It appears that the senses entrap us into error by their deceptive similitudes."
I answer that, Falsity is not to be sought in the senses except as truth is in them. Now truth is not in them in such a way as that the senses know truth, but in so far as they apprehend sensible things truly, as said above (Q[16], A[2]), and this takes place through the senses apprehending things as they are, and hence it happens that falsity exists in the senses through their apprehending or judging things to be otherwise than they really are.
The knowledge of things by the senses is in proportion to the existence of their likeness in the senses; and the likeness of a thing can exist in the senses in three ways. In the first way, primarily and of its own nature, as in sight there is the likeness of colors, and of other sensible objects proper to it. Secondly, of its own nature, though not primarily; as in sight there is the likeness of shape, size, and of other sensible objects common to more than one sense. Thirdly, neither primarily nor of its own nature, but accidentally, as in sight, there is the likeness of a man, not as man, but in so far as it is accidental to the colored object to be a man.
Sense, then, has no false knowledge about its proper objects, except accidentally and rarely, and then, because of the unsound organ it does not receive the sensible form rightly; just as other passive subjects because of their indisposition receive defectively the impressions of the agent. Hence, for instance, it happens that on account of an unhealthy tongue sweet seems bitter to a sick person. But as to common objects of sense, and accidental objects, even a rightly disposed sense may have a false judgment, because it is referred to them not directly, but accidentally, or as a consequence of being directed to other things.
Reply to Objection 1: The affection of sense is its sensation itself. Hence, from the fact that sense reports as it is affected, it follows that we are not deceived in the judgment by which we judge that we experience sensation. Since, however, sense is sometimes affected erroneously of that object, it follows that it sometimes reports erroneously of that object; and thus we are deceived by sense about the object, but not about the fact of sensation.
Reply to Objection 2: Falsity is said not to be proper to sense, since sense is not deceived as to its proper object. Hence in another translation it is said more plainly, "Sense, about its proper object, is never false." Falsity is attributed to the imagination, as it represents the likeness of something even in its absence. Hence, when anyone perceives the likeness of a thing as if it were the thing itself, falsity results from such an apprehension; and for this reason the Philosopher says (Metaph. v, 34) that shadows, pictures, and dreams are said to be false inasmuch as they convey the likeness of things that are not present in substance.
Reply to Objection 3: This argument proves that the false is not in the sense, as in that which knows the true and the false.
Objection 1: It seems that falsity is not in the intellect. For Augustine says (Qq. lxxxiii, 32), "Everyone who is deceived, understands not that in which he is deceived." But falsity is said to exist in any knowledge in so far as we are deceived therein. Therefore falsity does not exist in the intellect.
Objection 2: Further, the Philosopher says (De Anima iii, 51) that the intellect is always right. Therefore there is no falsity in the intellect.
On the contrary, It is said in De Anima iii, 21,[22] that "where there is composition of objects understood, there is truth and falsehood." But such composition is in the intellect. Therefore truth and falsehood exist in the intellect.
I answer that, Just as a thing has being by its proper form, so the knowing faculty has knowledge by the likeness of the thing known. Hence, as natural things cannot fall short of the being that belongs to them by their form, but may fall short of accidental or consequent qualities, even as a man may fail to possess two feet, but not fail to be a man; so the faculty of knowing cannot fail in knowledge of the thing with the likeness of which it is informed; but may fail with regard to something consequent upon that form, or accidental thereto. For it has been said (A[2]) that sight is not deceived in its proper sensible, but about common sensibles that are consequent to that object; or about accidental objects of sense. Now as the sense is directly informed by the likeness of its proper object, so is the intellect by the likeness of the essence of a thing. Hence the intellect is not deceived about the essence of a thing, as neither the sense about its proper object. But in affirming and denying, the intellect may be deceived, by attributing to the thing of which it understands the essence, something which is not consequent upon it, or is opposed to it. For the intellect is in the same position as regards judging of such things, as sense is as to judging of common, or accidental, sensible objects. There is, however, this difference, as before mentioned regarding truth (Q[16], A[2]), that falsity can exist in the intellect not only because the intellect is conscious of that knowledge, as it is conscious of truth; whereas in sense falsity does not exist as known, as stated above (A[2]).
But because falsity of the intellect is concerned essentially only with the composition of the intellect, falsity occurs also accidentally in that operation of the intellect whereby it knows the essence of a thing, in so far as composition of the intellect is mixed up in it. This can take place in two ways. In one way, by the intellect applying to one thing the definition proper to another; as that of a circle to a man. Wherefore the definition of one thing is false of another. In another way, by composing a definition of parts which are mutually exclusive. For thus the definition is not only false of the thing, but false in itself. A definition such as " a reasonable four-footed animal" would be of this kind, and the intellect false in making it; for such a statement as "some reasonable animals are four-footed" is false in itself. For this reason the intellect cannot be false in its knowledge of simple essences; but it is either true, or it understands nothing at all.
Reply to Objection 1: Because the essence of a thing is the proper object of the intellect, we are properly said to understand a thing when we reduce it to its essence, and judge of it thereby; as takes place in demonstrations, in which there is no falsity. In this sense Augustine's words must be understood, "that he who is deceived, understands not that wherein he is deceived;" and not in the sense that no one is ever deceived in any operation of the intellect.
Reply to Objection 2: The intellect is always right as regards first principles; since it is not deceived about them for the same reason that it is not deceived about what a thing is. For self-known principles are such as are known as soon as the terms are understood, from the fact that the predicate is contained in the definition of the subject.
Objection 1: It seems that true and false are not contraries. For true and false are opposed, as that which is to that which is not; for "truth," as Augustine says (Soliloq. ii, 5), "is that which is." But that which is and that which is not are not opposed as contraries. Therefore true and false are not contrary things.
Objection 2: Further, one of two contraries is not in the other. But falsity is in truth, because, as Augustine says, (Soliloq. ii, 10), "A tragedian would not be a false Hector, if he were not a true tragedian." Therefore true and false are not contraries.
Objection 3: Further, in God there is no contrariety, for "nothing is contrary to the Divine Substance," as Augustine says (De Civ. Dei xii, 2). But falsity is opposed to God, for an idol is called in Scripture a lie, "They have laid hold on lying" (Jer. 8:5), that is to say, "an idol," as a gloss says. Therefore false and true are not contraries.
On the contrary, The Philosopher says (Peri Herm. ii), that a false opinion is contrary to a true one.
I answer that, True and false are opposed as contraries, and not, as some have said, as affirmation and negation. In proof of which it must be considered that negation neither asserts anything nor determines any subject, and can therefore be said of being as of not-being, for instance not-seeing or not-sitting. But privation asserts nothing, whereas it determines its subject, for it is "negation in a subject," as stated in Metaph. iv, 4: v. 27; for blindness is not said except of one whose nature it is to see. Contraries, however, both assert something and determine the subject, for blackness is a species of color. Falsity asserts something, for a thing is false, as the Philosopher says (Metaph. iv, 27), inasmuch as something is said or seems to be something that it is not, or not to be what it really is. For as truth implies an adequate apprehension of a thing, so falsity implies the contrary. Hence it is clear that true and false are contraries.
Reply to Objection 1: What is in things is the truth of the thing; but what is apprehended, is the truth of the intellect, wherein truth primarily resides. Hence the false is that which is not as apprehended. To apprehend being, and not-being, implies contrariety; for, as the Philosopher proves (Peri Herm. ii), the contrary of this statement "God is good," is, "God is not good."
Reply to Objection 2: Falsity is not founded in the truth which is contrary to it, just as evil is not founded in the good which is contrary to it, but in that which is its proper subject. This happens in either, because true and good are universals, and convertible with being. Hence, as every privation is founded in a subject, that is a being, so every evil is founded in some good, and every falsity in some truth.
Reply to Objection 3: Because contraries, and opposites by way of privation, are by nature about one and the same thing, therefore there is nothing contrary to God, considered in Himself, either with respect to His goodness or His truth, for in His intellect there can be nothing false. But in our apprehension of Him contraries exist, for the false opinion concerning Him is contrary to the true. So idols are called lies, opposed to the divine truth, inasmuch as the false opinion concerning them is contrary to the true opinion of the divine unity.