Aquinas’ main discussions of the notion of truth are to be found in his commentary to Peter Lombard’s Sentences, in his Quaestiones disputatae de veritate and in his Summa theologiae (ST) Ia, question 16 (for the sake of coherence, here we shall focus on this latter text; for the different stages of development of Aquinas’ notion of truth, see Wippel 1989). His concept of truth can be seen as reconciling two important trends (see Wippel 1989:295 and Aertsen 1992), the neoplatonic-Augustinian conception attributing truth to things, and the Aristotelian conception (stemming from the Metaphysics) that attributes truth to the intellect and emphasizes truth as likeness.
Aquinas’ notion of truth is based on the concept of adequatio: truth is adequation of intellect and object. The etymology of adequation is related to that of equal, and indeed the idea here is that of quasi-equality between intellect and object. Adequation in this sense corresponds to identity of forms: truth occurs when the object and the concept in question share the same form. Truth is thus again viewed as a relational property, as in modern correspondence theories of truth, but this time it involves concepts and objects instead of propositions and facts as its relata. Aquinas does discuss the truth ofpropositions as well (in STIa q. 16 a. 8 ad 3), but their truth is derivative from truth in the intellect.
This relation of adequation is established by an act of the intellect, and can be established in two directions: an object is true if it conforms to the relevant concept, whereas a concept is true if it conforms to the relevant object (see Kiinne 2003:104). (Notice that, for Anselm, only the direction of adequation from object to (divine) concept characterizes the notion of truth.) These two directions are exactly what Aquinas needs to reconcile the two radically different approaches to truth that he takes as his starting point, namely truth of the intellect and truth of a thing; see Aertsen (1992:163/4).
Aquinas maintains that ‘‘truth resides primarily in the intellect, and secondarily in things according as they are related to the intellect as their principle’’ (STIa q. 16 a. 1 co.), so concepts are in fact the primary bearers of truth for him. An object can be said to be true by analogy, insofar as it is related to a true concept (i. e., one that conforms to the object); but an object is also true if it conforms to the design of the intellect behind its creation. Natural things are true insofar as they conform to the forms they have in the divine intellect. Similarly, artifacts are true if conformity occurs with the form they have (the original concept) in a human intellect (such as the relation of the plan of a house made by an architect and the house actually built). In both directions, properties of things define the truth of an entity (be it a concept or an object); Aquinas’ notion of truth is thus fundamentally metaphysical. Moreover, Aquinas develops his notion of truth against the background of his doctrine of transcendentals (see entry in this on Transcendentals): truth and being are ultimately convertible (Aertsen 1992: sect. 6).
There are two kinds of truths, the immutable truth of God and the finite truth of humans (ST cf. Ia q. 16 a. 8 co.). In the case of the finite truth of humans, the truth of concepts insofar as they represent objects corresponds to the direction of adequation from concepts to objects. By means of an act of predication (composition, in case of an affirmation, or division, in the case of a negation), a certain property is attributed to an object by the intellect; if the object is indeed such-and-such, then the concept representing it can be said to be true: ‘‘the being of the thing, not its truth, is the cause of truth in the intellect’’ (ST Ia q. 16 a. 1 ad 3). This kind of truth is referred to by Aquinas as accidental truth (per accidens), which is the truth pertaining to the knower who knows an object but upon whom the object does not depend (see Aertsen 1992:162). It is opposed to the essential truth (per se) of the divine intellect that designs and represents all natural things (since God is their creator) and of the human intellect with respect to artifacts (cf. ST Ia q. 16 a. 1 co.). Obviously, given God’s perfection, adequation of concepts in the divine intellect to things in an accidental way simply does not occur. Only essential truth pertains to the divine intellect, and accidental truth is proper to finite human knowers.
Indeed, God is ultimately Truth itself for Aquinas (Ia q. 16 a. 5 co.): truth is adequation of intellect and being, and in God this adequation occurs ‘‘to the greatest degree.’’ In God there is total coincidence of intellect and being, as the forms present in the divine intellect are the very causes of the forms present in each object of His creation. ‘‘His being is not only conformed to His intellect, but it is the very act of His intellect; and His act of understanding is the measure and cause of every other being and of every other intellect’’.
World History
