Thomas Aquinas

“ Understanding is the fruit of faith, taken as a virtue. But we are not taking faith in this sense here, but for a kind of certitude of faith, to which man attains by the gift of understanding.
Reply to Objection 2: Faith cannot altogether precede understanding, for it would be impossible to assent by believing what is proposed to be believed, without understanding it in some way. However, the perfection of understanding follows the virtue of faith: which perfection of understanding is itself followed by a kind of certainty of faith. ”

“ The excellence of the gift of understanding consists precisely in its considering eternal or necessary matters, not only as they are rules of human actions, because a cognitive virtue is the more excellent, according to the greater extent of its object. ”

“ The things with which human actions are concerned are not surpassingly exalted considered in themselves, but, as referred to the rule of the eternal law, and to the end of Divine happiness, they are exalted so that they can be the matter of understanding. ”

“ Secondly, it is necessary that man should judge these things aright, that he should esteem that he ought to adhere to these things, and to withdraw from their opposites: and this judgment, with regard to Divine things belong to the gift of wisdom, but with regard to created things, belongs to the gift of knowledge, and as to its application to individual actions, belongs to the gift of counsel. ”

“ The reason why there are several fruits pertaining to the appetitive faculty, is because, as already stated, the character of end, which the word fruit implies, pertains to the appetitive rather than to the intellective part. ”