Thomas Aquinas

“ It is unlawful to desire vengeance considered as evil to the man who is to be punished, but it is praiseworthy to desire vengeance as a corrective of vice and for the good of justice; and to this the sensitive appetite can tend, in so far as it is moved thereto by the reason: and when revenge is taken in accordance with the order of judgment, it is God's work, since he who has power to punish "is God's minister," as stated in Rom. ”

“ Although hatred sometimes arises from anger, it has a previous cause, from which it arises more directly, namely displeasure, even as, on the other hand, love is born of pleasure. Now through displeasure, a man is moved sometimes to anger, sometimes to hatred. Wherefore it was fitting to reckon that hatred arises from sloth rather than from anger. ”

“ Anger is stated to be the door to the vices accidentally, that is by removing obstacles, to wit by hindering the judgment of reason, whereby man is withdrawn from evil. It is, however, directly the cause of certain special sins, which are called its daughters. ”

“ On the other hand, if one desire the taking of vengeance in any way whatever contrary to the order of reason, for instance if he desire the punishment of one who has not deserved it, or beyond his deserts, or again contrary to the order prescribed by law, or not for the due end, namely the maintaining of justice and the correction of defaults, then the desire of anger will be sinful, and this is called sinful anger. ”

“ Now this does not apply to anger, which is the desire for revenge, since revenge may be desired both well and ill. Secondly, evil is found in a passion in respect of the passion's quantity, that is in respect of its excess or deficiency; and thus evil may be found in anger, when, to wit, one is angry, more or less than right reason demands. But if one is angry in accordance with right reason, one's anger is deserving of praise. ”

“ Secondly, the movement of anger may be inordinate in the mode of being angry, for instance, if one be too fiercely angry inwardly, or if one exceed in the outward signs of anger. In this way anger is not a mortal sin in the point of its genus; yet it may happen to be a mortal sin, for instance if through the fierceness of his anger a man fall away from the love of God and his neighbor. ”

“ The other disorder is when a man breaks out into injurious words, and if these be against God, it is "blasphemy," if against one's neighbor, it is "contumely."
Thirdly, anger may be considered as proceeding to deeds; and thus anger gives rise to "quarrels," by which we are to understand all manner of injuries inflicted on one's neighbor through anger. ”

“ It does not follow from the passage quoted that all anger is a mortal sin, but that the foolish are killed spiritually by anger, because, through not checking the movement of anger by their reason, they fall into mortal sins, for instance by blaspheming God or by doing injury to their neighbor. ”

“ It is in this sense that Jerome considers anger; for he speaks of the anger whereby one is angry with one's neighbor, with the intent of doing him a wrong.---But, according to the Peripatetics, to whose opinion Augustine inclines (De Civ. Dei ix, 4) , anger and the other passions of the soul are movements of the sensitive appetite, whether they be moderated or not, according to reason: and in this sense anger is not always evil. ”

“ In another way, it happens on the part of vengeance, which a man seeks with a stubborn desire: this applies to "ill-tempered" or "stern" people, who do not put aside their anger until they have inflicted punishment. ”

“ But as regulated by reason, it may be something meritorious and deserving of praise; while on the other hand, as not regulated by reason, it may be demeritorious and blameworthy. Wherefore the Philosopher says (Ethic. ii, 5) that "it is he who is angry in a certain way, that is praised or blamed." ”