Thomas Aquinas

“ Anger, on the other hand, seeks evil only under the aspect of a just means of vengeance. Consequently when the evil inflicted goes beyond the measure of justice according to the estimate of the angry man, then he has mercy. Wherefore the Philosopher says (Rhet. ii, 4) that "the angry man is appeased if many evils befall, whereas the hater is never appeased."
As to the intensity of the desire, anger excludes mercy more than hatred does; because the movement of anger is more impetuous, through the heating of the bile. ”

“ Cicero gives the name of desire to any kind of craving for a future good, without discriminating between that which is arduous and that which is not. Accordingly he reckons anger as a kind of desire, inasmuch as it is a desire of vengeance. In this sense, however, desire is common to the irascible and concupiscible faculties. ”

“ And if we consider the nature of the individual, in respect of his particular temperament, thus anger is more natural than desire; for the reason that anger is prone to ensue from the natural tendency to anger, more than desire, or any other passion, is to ensue from a natural tendency to desire, which tendencies result from a man's individual temperament. ”

“ It would seem that anger does not require an act of reason. For, since anger is a passion, it is in the sensitive appetite. But the sensitive appetite follows an apprehension, not of reason, but of the sensitive faculty. ”

“ First, by way of an incomplex object, as when we understand what a man is; secondly, by way of a complex object, as when we understand that whiteness is in a man. Consequently in each of these ways the appetitive power can tend to both good and evil: by way of a simple and incomplex object, when the appetite simply follows and adheres to good, or recoils from evil: and such movements are desire, hope, pleasure, sorrow, and so forth: by way of a complex object, as when the appetite is concerned with some good or evil being in, or being done to, another, either seeking this or recoiling from it. ”

“ Since then in man there is both reason and imagination, the movement of anger can be aroused in man in two ways. First, when only his imagination denounces the injury: and, in this way, man is aroused to a movement of anger even against irrational and inanimate beings, which movement is like that which occurs in animals against anything that injures them. ”

“ But, in a third way, anger may be called a general passion, inasmuch as it is caused by a concurrence of several passions. Because the movement of anger does not arise save on account of some pain inflicted, and unless there be desire and hope of revenge: for, as the Philosopher says (Rhet. ii, 2) , "the angry man hopes to punish; since he craves for revenge as being possible." ”

“ But other animals, for as much as their temperament recedes from this moderation and approaches to an extreme disposition, are naturally disposed to some excess of passion, such as the lion in daring, the hound in anger, the hare in fear, and so forth. On the part of reason, however, it is natural to man, both to be angry and to be gentle: in so far as reason somewhat causes anger, by denouncing the injury which causes anger ”

“ Because just as a genus contains potentially many differences, according to a likeness of matter; so an efficient cause contains many effects according to its active power. Now it happens that an effect is produced by the concurrence of various causes; and since every cause remains somewhat in its effect, we may say that, in yet a third way, an effect which is due to the concurrence of several causes, has a certain generality, inasmuch as several causes are, in a fashion, actually existing therein. ”

“ For since hatred desires another's evil for evil's sake, it is satisfied with no particular measure of evil: because those things that are desired for their own sake, are desired without measure, as the Philosopher states (Polit. i, 3) , instancing a miser with regard to riches. ”