to hate whatever is contrary to it, and to aim at its undoing.
Therefore it seems that it is not a sin to hate one's I enemy.

_On the contrary,_ It is written (1 John 2:9): "He that . . . hateth
his brother, is in darkness." Now spiritual darkness is sin.
Therefore there cannot be hatred of one's neighbor without sin.

_I answer that,_ Hatred is opposed to love, as stated above (I-II, Q.
29, A. 2); so that hatred of a thing is evil according as the love of
that thing is good. Now love is due to our neighbor in respect of
what he holds from God, i.e. in respect of nature and grace, but not
in respect of what he has of himself and from the devil, i.e. in
respect of sin and lack of justice.

Consequently it is lawful to hate the sin in one's brother, and
whatever pertains to the defect of Divine justice, but we cannot hate
our brother's nature and grace without sin. Now it is part of our
love for our brother that we hate the fault and the lack of good in
him, since desire for another's good is equivalent to hatred of his
evil. Consequently the hatred of one's brother, if we consider it
simply, is always sinful.

Reply Obj. 1: By the commandment of God (Ex. 20:12) we must honor our
parents--as united to us in nature and kinship. But we must hate them
in so far as they prove an obstacle to our attaining the perfection
of Divine justice.

Reply Obj. 2: God hates the sin which is in the detractor, not his
nature: so that we can hate detractors without committing a sin.

Reply Obj. 3: Men are not opposed to us in respect of the goods which
they have received from God: wherefore, in this respect, we should
love them. But they are opposed to us, in so far as they show
hostility towards us, and this is sinful in them. In this respect we
should hate them, for we should hate in them the fact that they are
hostile to us.
_______________________

FOURTH ARTICLE [II-II, Q. 34, Art. 4]

Whether Hatred of Our Neighbor Is the Most Grievous Sin Against Our
Neighbor?

Objection 1: It would seem that hatred of our neighbor is the most
grievous sin against our neighbor. For it is written (1 John 3:15):
"Whosoever hateth his brother is a murderer." Now murder is the most
grievous of sins against our neighbor. Therefore hatred is also.

Obj. 2: Further, worst is opposed to best. Now the best thing we give
our neighbor is love, since all other things are referable to love.
Therefore hatred is the worst.

_On the contrary,_ A thi