On the contrary, The Philosopher says (Rhet. ii, 2) that anger is "a desire, with sorrow, for vengeance, on account of a seeming slight done unbecomingly."
I answer that, All the causes of anger are reduced to slight. For slight is of three kinds, as stated in Rhet. ii, 2, viz. "contempt," "despiteful treatment," i.e. hindering one from doing one's will, and "insolence": and all motives of anger are reduced to these three. Two reasons may be assigned for this. First, because anger seeks another's hurt as being a means of just vengeance: wherefore it seeks vengeance in so far as it seems just. Now just vengeance is taken only for that which is done unjustly; hence that which provokes anger is always something considered in the light of an injustice. Wherefore the Philosopher says (Rhet. ii, 3) that "men are not angry,—if they think they have wronged some one and are suffering justly on that account; because there is no anger at what is just." Now injury is done to another in three ways: namely, through ignorance, through passion, and through choice. Then, most of all, a man does an injustice, when he does an injury from choice, on purpose, or from deliberate malice, as stated in Ethic. v, 8. Wherefore we are most of all angry with those who, in our opinion, have hurt us on purpose. For if we think that some one has done us an injury through ignorance or through passion, either we are not angry with them at all, or very much less: since to do anything through ignorance or through passion takes away from the notion of injury, and to a certain extent calls for mercy and forgiveness. Those, on the other hand, who do an injury on purpose, seem to sin from contempt; wherefore we are angry with them most of all. Hence the Philosopher says (Rhet. ii, 3) that "we are either not angry at all, or not very angry with those who have acted through anger, because they do not seem to have acted slightingly."
The second reason is because a slight is opposed to a man's excellence: because "men think little of things that are not worth much ado" (Rhet. ii, 2). Now we seek for some kind of excellence from all our goods. Consequently whatever injury is inflicted on us, in so far as it is derogatory to our excellence, seems to savor of a slight.
Reply Obj. 1: Any other cause, besides contempt, through which a man suffers an injury, takes away from the notion of injury: contempt or slight alone adds to the motive of anger, and consequently is of itself the cause of anger.
Reply Obj. 2: Although a dumb animal does not seek honor as such, yet it naturally seeks a certain superiority, and is angry with anything derogatory thereto.
Reply Obj. 3: Each of those causes amounts to some kind of slight. Thus forgetfulness is a clear sign of slight esteem, for the more we think of a thing the more is it fixed in our memory. Again if a man does not hesitate by his remarks to give pain to another, this seems to show that he thinks little of him: and those too who show signs of hilarity when another is in misfortune, seem to care little about his good or evil. Again he that hinders another from carrying out his will, without deriving thereby any profit to himself, seems not to care much for his friendship. Consequently all those things, in so far as they are signs of contempt, provoke anger. ________________________
THIRD ARTICLE [I-II, Q. 47, Art. 3]
Whether a Man's Excellence Is the Cause of His Being Angry?
Objection 1: It would seem that a man's excellence is not the cause of his being more easily angry. For the Philosopher says (Rhet. ii, 2) that "some are angry especially when they are grieved, for instance, the sick, the poor, and those who are disappointed." But these things seem to pertain to defect. Therefore defect rather than excellence makes one prone to anger.
Obj. 2: Further, the Philosopher says (Rhet. ii, 2) that "some are very much inclined to be angry when they are despised for some failing or weakness of the existence of which there are grounds for suspicion; but if they think they excel in those points, they do not trouble." But a suspicion of this kind is due to some defect. Therefore defect rather than excellence is a cause of a man being angry.