I answer that, As stated above (A. 2), anger is a desire for vengeance. Now vengeance implies a comparison between the punishment to be inflicted and the hurt done; wherefore the Philosopher says (Ethic. vii, 6) that "anger, as if it had drawn the inference that it ought to quarrel with such a person, is therefore immediately exasperated." Now to compare and to draw an inference is an act of reason. Therefore anger, in a fashion, requires an act of reason.
Reply Obj. 1: The movement of the appetitive power may follow an act of reason in two ways. In the first way, it follows the reason in so far as the reason commands: and thus the will follows reason, wherefore it is called the rational appetite. In another way, it follows reason in so far as the reason denounces, and thus anger follows reason. For the Philosopher says (De Problem. xxviii, 3) that "anger follows reason, not in obedience to reason's command, but as a result of reason's denouncing the injury." Because the sensitive appetite is subject to the reason, not immediately but through the will.
Reply Obj. 2: Dumb animals have a natural instinct imparted to them by the Divine Reason, in virtue of which they are gifted with movements, both internal and external, like unto rational movements, as stated above (Q. 40, A. 3).
Reply Obj. 3: As stated in Ethic. vii, 6, "anger listens somewhat to reason" in so far as reason denounces the injury inflicted, "but listens not perfectly," because it does not observe the rule of reason as to the measure of vengeance. Anger, therefore, requires an act of reason; and yet proves a hindrance to reason. Wherefore the Philosopher says (De Problem. iii, 2, 27) that whose who are very drunk, so as to be incapable of the use of reason, do not get angry: but those who are slightly drunk, do get angry, through being still able, though hampered, to form a judgment of reason. ________________________
FIFTH ARTICLE [I-II, Q. 46, Art. 5]
Whether Anger Is More Natural Than Desire?
Objection 1: It would seem that anger is not more natural than desire. Because it is proper to man to be by nature a gentle animal. But "gentleness is contrary to anger," as the Philosopher states (Rhet. ii, 3). Therefore anger is no more natural than desire, in fact it seems to be altogether unnatural to man.
Obj. 2: Further, reason is contrasted with nature: since those things that act according to reason, are not said to act according to nature. Now "anger requires an act of reason, but desire does not," as stated in Ethic. vii, 6. Therefore desire is more natural than anger.
Obj. 3: Further, anger is a craving for vengeance: while desire is a craving for those things especially which are pleasant to the touch, viz. for pleasures of the table and for sexual pleasures. But these things are more natural to man than vengeance. Therefore desire is more natural than anger.
On the contrary, The Philosopher says (Ethic. vii, 6) that "anger is more natural than desire."