HKB
(Enchiridion xii). Now there are sins by which a man hurts his neighbor more than by hatred, e.g. theft, murder and adultery. Therefore hatred is not the most grievous sin.
Moreover, Chrysostom [*Hom. x in the Opus Imperfectum, falsely ascribed to St. John Chrysostom] commenting on Matt. 5:19, "He that shall break one of these least commandments," says: "The commandments of Moses, Thou shalt not kill, Thou shalt not commit adultery, count for little in their reward, but they count for much if they be disobeyed. On the other hand the commandments of Christ such as, Thou shalt not be angry, Thou shalt not desire, are reckoned great in their reward, but little in the transgression." Now hatred is an internal movement like anger and desire. Therefore hatred of one's brother is a less grievous sin than murder.
I answer that, Sins committed against our neighbor are evil on two counts; first by reason of the disorder in the person who sins, secondly by reason of the hurt inflicted on the person sinned against. On the first count, hatred is a more grievous sin than external actions that hurt our neighbor, because hatred is a disorder of man's will, which is the chief part of man, and wherein is the root of sin, so that if a man's outward actions were to be inordinate, without any disorder in his will, they would not be sinful, for instance, if he were to kill a man, through ignorance or out of zeal for justice: and if there be anything sinful in a man's outward sins against his neighbor, it is all to be traced to his inward hatred.
On the other hand, as regards the hurt inflicted on his neighbor, a man's outward sins are worse than his inward hatred. This suffices for the Replies to the Objections.
FIFTH ARTICLE [II-II, Q. 34, Art. 5]
Whether Hatred Is a Capital Sin?
Objection 1: It would seem that hatred is a capital sin. For hatred is directly opposed to charity. Now charity is the foremost among the virtues, and the mother of all others. Therefore hatred is the chief of the capital sins, and the origin of all others.
Obj. 2: Further, sins arise in us on account of the inclinations of our passions, according to Rom. 7:5: "The passions of sins . . . did work in our members to bring forth fruit unto death." Now all other passions of the soul seem to arise from love and hatred, as was shown above (I-II, Q. 25, AA. 1, 2). Therefore hatred should be reckoned one of the capital sins.
Obj. 3: Further, vice is a moral evil. Now hatred regards evil more than any other passion does. Therefore it seems that hatred should be reckoned a capital sin.
On the contrary, Gregory (Moral. xxxi) does not reckon hatred among the seven capital sins.
I answer that, As stated above (I-II, Q. 84, AA. 3, 4), a capital vice is one from which other vices arise most frequently. Now vice is contrary to man's nature, in as much as he is a rational animal: and when a thing acts contrary to its nature, that which is natural to it is corrupted little by little. Consequently it must first of all fail in that which is less in accordance with its nature, and last of all in that which is most in accordance with its nature, since what is first in construction is last in destruction. Now that which, first and foremost, is most natural to man, is the love of what is good, and especially love of the Divine good, and of his neighbor's good. Wherefore hatred, which is opposed to this love, is not the first but the last thing in the downfall of virtue resulting from vice: and therefore it is not a capital vice.