Magisterium AI

Disputed Questions on Truth

  • Thomas Aquinas
  • 1256 AD
  • Theological Work
Source. Translated by Robert W. Mulligan, SJ, from the definitive Leonine text (Henry Regnery Company, 1952)

On Truth - What is truth?

Q. 1, A. 1, C.Response: When investigating the nature of anything, one should make the same kind of analysis as he makes when he reduces a proposition to certain self-evident principles. Otherwise, both types of knowledge will become involved in an infinite regress, and science and our knowledge of things will perish. Now, as Avicenna says, that which the intellect first conceives as, in a way, the most evident, and to which it reduces all its concepts, is being. Consequently, all the other conceptions of the intellect are had by additions to being. But nothing can be added to being as though it were something not included in being—in the way that a difference is added to a genus or an accident to a subject—for every reality is essentially a being. The Philosopher has shown this by proving that being cannot be a genus. Yet, in this sense, some predicates may be said to add to being inasmuch as they express a mode of being not expressed by the term "being." This happens in two ways. First, the mode expressed is a certain special manner of being; for there are different grades of being according to which we speak when we speak of different levels of existence, and according to these grades different things are classified. Consequently, "substance" does not add a difference to being by signifying some reality added to it, but "substance" simply expresses a special manner of existing, namely, as a being in itself. The same is true of the other classes of existents. Second, some are said to add to being because the mode they express is one that is common, and consequent upon every being. This mode can be taken in two ways: first, in so far as it follows upon every being considered absolutely; second, in so far as it follows upon every being considered in relation to another. In the first, the term is used in two ways, because it expresses something in the being either affirmatively or negatively. We can, however, find nothing that can be predicated of every being affirmatively and, at the same time, absolutely, with the exception of its essence by which the being is said to be. To express this, the term "thing" is used; for, according to Avicenna, thing differs from being because being gets its name from to-be, but thing expresses the quiddity or essence of the being. There is, however, a negation consequent upon every being considered absolutely: its undividedness, and this is expressed by "one." For the "one" is simply undivided being. If the mode of being is taken in the second way—according to the relation of one being to another—we find a twofold use. The first is based on the distinction of one being from another, and this distinctness is expressed by the word "something," which implies, as it were, "some other thing." For, just as a being is said to be "one" in so far as it is without division in itself, so it is said to be "something" in so far as it is divided from others. The second division is based on the correspondence one being has with another. This is possible only if there is something which is such that it agrees with every being. Such a being is the soul, which, as is said in The Soul, in some way is all things. The soul, however, has both knowing and appetitive powers. "Good" expresses the correspondence of being to the appetitive power, for, and so we note in the Ethics, the good is that which all desire. "True" expresses the correspondence of being to the knowing power, for all knowing is produced by an assimilation of the knower to the thing known, so that assimilation is said to be the cause of knowledge. Similarly, the sense of sight knows a color by being informed with a species of the color. The first reference of being to the intellect, therefore, consists in its agreement with the intellect. This agreement is called “the conformity of thing and intellect.” In this conformity is fulfilled the formal constituent of the true, and this is what "the true" adds to being, namely, the conformity or equation of thing and intellect. As we said, the knowledge of a thing is a consequence of this conformity; therefore, it is an effect of truth, even though the fact that the thing is a being is prior to its truth. Consequently, truth or the true has been defined in three ways. First of all, it is defined according to that which precedes truth and is the basis of truth. This is why Augustine writes: the true is that which is; and Avicenna: the truth of each thing is a property of the act of being which has been established for it. Still others say: the true is the undividedness of the act of existence from that which is. Truth is also defined in another way—according to that in which its intelligible determination is formally completed. Thus, Isaac writes: truth is the conformity of thing and intellect; and Anselm: truth is a rectitude perceptible only by the mind. This rectitude, of course, is said to be based on some conformity. The Philosopher says that in defining truth we say that truth is had when one affirms that to be which is, and that not to be which is not. The third way of defining truth is according to the effect following upon it. Thus, Hilary says that the true is that which manifests and proclaims existence. And Augustine says: truth is that by which that which is, is shown; and also: truth is that according to which we judge about inferior things. Reply Obj. 1: That definition of Augustine is given for the true as it has its foundation in reality and not as its formal nature is given complete expression by conformity of thing and intellect. An alternative answer would be that in the statement, “The true is that which is,” the word "is" is not here understood as referring to the act of existing, but rather as the mark of the intellectual act of judging, signifying, that is, the affirmation of a proposition. The meaning would then be this: “The true is that which is—it is had when the existence of what is, is affirmed.” If this is its meaning, then Augustine’s definition agrees with that of the Philosopher mentioned above. Reply Obj. 2: The answer is clear from what has been said. Reply Obj. 3: “Something can be understood without another” can be taken in two ways. It can mean that something can be known while another remains unknown. Taken in this way, it is true that things which differ conceptually are such that one can be understood without the other. But there is another way that a thing can be understood without another: when it is known even though the other does not exist. Taken in this sense, being cannot be known without the true, for it cannot be known unless it agrees with or conforms to intellect, It is not necessary, however, that everyone who understands the formal notion of being should also understand the formal notion of the true—just as not everyone who understands being understands the agent intellect, even though nothing can be known without the agent intellect. Reply Obj. 4: The true is a state of being even though it does not add any reality to being or express any special mode of existence. It is rather something that is generally found in every being, although it is not expressed by the word "being." Consequently, it is not a state that corrupts, limits, or contracts. Reply Obj. 5: In this objection, "condition" should not be understood as belonging to the genus of quality. It implies, rather, a certain order; for those which are the cause of the existence of other things are themselves beings most completely, and those which are the cause of the truth of other things are themselves true most completely. It is for this reason that the Philosopher concludes that the rank of a thing in its existence corresponds to its rank in truth, so that when one finds that which is most fully being, he finds there also that which is most fully true. But this does not mean that being and the true are the same in concept. It means simply that in the degree in which a thing has being, in that degree it is capable of being proportioned to intellect. Consequently, the true is dependent upon the formal character of being. Reply Obj. 6: There is a conceptual difference between the true and being since there is something in the notion of the true that is not in the concept of the existing—not in such a way, however, that there is something in the concept of being which is not in the concept of the true. They do not differ essentially nor are they distinguished from one another by opposing differences. Reply Obj. 7: The true does not have a wider extension than being. Being is, in some way, predicated of non-being in so far as non-being is apprehended by the intellect. For, as the Philosopher says, the negation or the privation of being may, in a sense, be called being. Avicenna supports this by pointing out that one can form propositions only of beings, for that about which a proposition is formed must be apprehended by the intellect. Consequently, it is clear that everything true is being in some way. Reply Sed Contra 1: It must be said that the reason why it is not tautological to call a being true is that something is expressed by the word "true" that is not expressed by the word "being," and not that the two differ in reality. Reply Sed Contra 2: Although fornication is evil, it possesses some being and can conform to intellect. Accordingly, the formal character of the true is found here. So it is clear that "true" is coextensive with "being." Reply Sed Contra 3: In the statement, to be is other than that which is, the act of being is distinguished from that to which that act belongs. But the name of being is taken from the act of existence, not from that whose act it is. Hence, the argument does not follow. Reply Sed Contra 4: The true comes after being in this respect, that the notion of the true differs from that of being in the manner we have described. Reply Sed Contra 5: This argument has three flaws. First, although the Persons are really distinct, the things appropriated to each Person are only conceptually, and not really, distinct. Secondly, although the Persons are really distinct from each other, they are not really distinct from the essence; so, truth appropriated to the Person of the Son is not distinct from the act of existence He possesses through the divine essence. Thirdly, although being, the true, the one, and the good are more united in God than they are in created things, it does not follow from the fact that they are conceptually distinct in God that they are really distinct in created beings. This line of argument is valid only when it is applied to things which are not by their very nature one in reality, as wisdom and power, which, although one in God, are distinct in creatures. But being, the true, the one, and the good are such that by their very nature they are one in reality. Therefore, no matter where they are found, they are really one. Their unity in God, however, is more perfect than their unity in creatures.