Thomas Aquinas

“ Secondly, by way of opposition, because a passion often inclines to something contrary to what man knows in general. Thirdly, by way of bodily transmutation, the result of which is that the reason is somehow fettered so as not to exercise its act freely; even as sleep or drunkenness, on account of some change wrought on the body, fetters the use of reason. That this takes place in the passions is evident from the fact that sometimes, when the passions are very intense, man loses the use of reason altogether: for many have gone out of their minds through excess of love or anger. ”

“ It may happen, then, that a man has some knowledge in general, e.g. that no fornication is lawful, and yet he does not know in particular that this act, which is fornication, must not be done; and this suffices for the will not to follow the universal knowledge of the reason. ”

“ Again, it must be observed that nothing prevents a thing which is known habitually from not being considered actually: so that it is possible for a man to have correct knowledge not only in general but also in particular, and yet not to consider his knowledge actually: and in such a case it does not seem difficult for a man to act counter to what he does not actually consider. ”

“ Concupiscence, whereby a man desires good for himself, is reduced to self-love as to its cause, as stated.
Reply to Objection 3: Man is said to love both the good he desires for himself, and himself to whom he desires it. Love, in so far as it is directed to the object of desire (e.g. a man is said to love wine or money) admits, as its cause, fear which pertains to avoidance of evil: for every sin arises either from inordinate desire for some good, or from inordinate avoidance of some evil. ”

“ One is natural, and is directed to those things which sustain the nature of the body, whether as regards the preservation of the individual, such as food, drink, and the like, or as regards the preservation of the species, such as sexual matters: and the inordinate appetite of such things is called "concupiscence of the flesh." The other is spiritual concupiscence, and is directed to those things which do not afford sustentation or pleasure in respect of the fleshly senses, but are delectable in respect of the apprehension or imagination, or some similar mode of perception ”

“ Sometimes man fails to consider actually what he knows habitually, on account of some hindrance supervening, e.g. some external occupation, or some bodily infirmity; and, in this way, a man who is in a state of passion, fails to consider in particular what he knows in general, in so far as the passions hinder him from considering it. ”

“ Hence it is written (Prov. 14:22) : "They err that work evil."
Experience, however, shows that many act contrary to the knowledge that they have, and this is confirmed by Divine authority, according to the words of Lk. 12:47: "The servant who knew that the will of his lord . . . and did not . . . shall be beaten with many stripes," and of James 4:17: "To him . . . who knoweth to do good, and doth it not, to him it is a sin." ”

“ Further, if it be said that it draws the reason from its knowledge of something in general, to form a contrary judgment about a particular matter---on the contrary, if a universal and a particular proposition be opposed, they are opposed by contradiction, e.g. "Every man," and "Not every man." ”

“ He that has knowledge in a universal, is hindered, on account of a passion, from reasoning about that universal, so as to draw the conclusion: but he reasons about another universal proposition suggested by the inclination of the passion, and draws his conclusion accordingly. Hence the Philosopher says (Ethic. vii, 3) that the syllogism of an incontinent man has four propositions, two particular and two universal, of which one is of the reason, e.g. ”