St. Thomas Aquinas, Commentary on Boethius’s De Trinitate, ch. 1, q. 3, a. 1, reply.

...faith has something in common with opinion, and something in common with knowledge and understanding, by reason of which it holds a position midway between opinion and understanding or science, according to Hugh of St. Victor. In common with understanding and knowledge, it possesses certain and fixed assent; and in this it differs from opinion, which accepts one of two opposites, though with fear that the other may be true, and on account of this doubt it fluctuates between two contraries. But, in common with opinion, faith is concerned with things that are not naturally possible to our understanding, and in this respect it differs from science and intellection.

That a thing should not be apparent to human understanding can arise for two reasons, as is said in II Metaph.: namely, (1) because of lack of knowability in things themselves, and (2) because of lack of intellectual ability on our part.

(1) It may be due to lack on the part of things, as in the case of singular and contingent things which are remote from our senses, like the deeds and words and thoughts of men; for these are of such a nature that they may be known to one man, but unknown to others. And since among men dwelling together one man should deal with another as with himself in what he is not self-sufficient, therefore it is needful that he be able to stand with as much certainty on what another knows, but of which he himself is ignorant, as upon the truths which he himself knows. Hence it is that in human society faith is necessary in order that one man give credence to the words of another, and this is the foundation of justice, as Tullius says in his book, De officiis. Hence also it is that no lie is without sin, since every lie derogates from that faith which is so necessary.

(2) The truth of things may also not be evident because of defect on our part, as in the case of divine and necessary things which, according to their own nature, are most knowable. Wherefore, to understand them, we are not capable of immediate intellection, from the very beginning, since it is in accordance with our nature to attain from things less knowable and posterior in themselves, to knowledge of those that are themselves more knowable and prior. But since from none of those things that we know last do we have any knowledge of those that we know first, it is needful for us even at first to have some notion of those things that are most knowable in themselves; but this cannot be except by believing. And this is evident even in the order of the sciences; since that science which is concerned with highest causes, namely, metaphysics, comes last in human knowledge; yet in sciences that are preambles to it there must be supposed certain truths which only in it are more fully revealed; therefore every science has some suppositions that must be believed in order to carry on the process of learning.

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Return to Lesson 12: What is Faith?