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Aquinas on Truth
Aquinas offers a version of a correspondence theory of truth which fits in with the ontological realism found in his philosophy of mind and in his epistemology. Often Aquinas considers truth as a ‘conformity’ (read ‘adequatio’) of mind and thing: ‘adequatio rei et intellectus’. In De Veritate, he writes as follows about the nature of truth:
Just as the true is found primarily in the intellect rather than in things, so also is it found primarily in an act of the intellect joining and separating, rather than in an act by which it forms the quiddities of things. For the nature of the true consists in conformity of thing and intellect. Nothing becomes conformed to itself, but conformity requires distinct terms. Consequently, the nature of truth is first found in the intellect when the intellect begins to possess something proper to itself, not possessed by the thing outside the soul, yet corresponding to it, so that between the two—intellect and thing—a conformity may be found. In forming the quiddities of things, the intellect merely has a likeness of a thing existing outside the soul, as a sense has a likeness when it receives the species of a sensible thing. But when the intellect begins to judge about the thing it has apprehended, then its judgement is something proper to itself—not something found outside in the thing. The judgement is said to be true when it conforms to the external reality. Moreover, the intellect judges about the thing it has apprehended at the moment when it says that something is or is not. This is the role of ‘the intellect composing and dividing’. (De Veritate, q. 1)
Scholastic philosophy often considered three acts of the mind:
The property of ‘true’ applies to subjects and predicates being ‘combined and divided’ in a way that corresponds to things in the external world. Hence, ‘true’ is a property of judgement. ‘Simple apprehension’ refers to the acquisition of a concept through the process of abstraction using the intellectus agens and the intellectus possi- bilis. The object of the awareness is a ‘quiddity’ or an ‘essence’ of a natural kind which is the result of abstraction using the intellectus agens and then the act of knowing of the intellectus possibilis. ‘Reasoning’ refers principally to the use of the Aristotelian syllogism where the rules of formal logic apply.
Aquinas also offers a distinction between what we might call ‘ontological truth’ and ‘formal’ or ‘epistemological’ truth. Ontological truth is the relation that holds between an exemplar in the Divine Mind and instances of that exemplar in the material world. For instance, one Divine Idea is the exemplar of human nature. Human beings are what they are, Aquinas argues using an Augustinian insight, because they are made in the ‘image and likeness of God, which is the correspondence of individual to the Divine Idea. Epistemological or formal truth holds when the idea in the human mind corresponds with the thing in the external world, in reference either to essential or accidental properties. In either case, truth is an ‘adequatio rei et intellectus’5
The next chapter will begin the explicatio textus of the relevant sections—taken, for the most part, from Aquinas’s Commentary on the Soul—that treat sensation and perception in detail. The author agrees with Pasnau’s judgement expressed in his translation of the Commentary: ‘The De Anima commentary is particularly important for understanding certain aspects of Aquinas’s philosophy. Here, more than anywhere else, Aquinas gives detailed accounts of the processes involved in human cognition.’  It is in the spirit of Professor Pasnau’s observations that the remainder of this study is directed.
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