issonance from that which opposes and destroys it; and
this is natural hatred. So, therefore, in the animal appetite, or in
the intellectual appetite, love is a certain harmony of the appetite
with that which is apprehended as suitable; while hatred is
dissonance of the appetite from that which is apprehended as
repugnant and hurtful. Now, just as whatever is suitable, as such,
bears the aspect of good; so whatever is repugnant, as such, bears
the aspect of evil. And therefore, just as good is the object of
love, so evil is the object of hatred.

Reply Obj. 1: Being, as such, has not the aspect of repugnance but
only of fittingness; because being is common to all things. But
being, inasmuch as it is this determinate being, has an aspect of
repugnance to some determinate being. And in this way, one being is
hateful to another, and is evil; though not in itself, but by
comparison with something else.

Reply Obj. 2: Just as a thing may be apprehended as good, when it is
not truly good; so a thing may be apprehended as evil, whereas it is
not truly evil. Hence it happens sometimes that neither hatred of
evil nor love of good is good.

Reply Obj. 3: To different things the same thing may be lovable or
hateful: in respect of the natural appetite, owing to one and the
same thing being naturally suitable to one thing, and naturally
unsuitable to another: thus heat is becoming to fire and unbecoming
to water: and in respect of the animal appetite, owing to one and
the same thing being apprehended by one as good, by another as bad.
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SECOND ARTICLE [I-II, Q. 29, Art. 2]

Whether Love Is a Cause of Hatred?

Objection 1: It would seem that love is not a cause of hatred. For
"the opposite members of a division are naturally simultaneous"
(Praedic. x). But love and hatred are opposite members of a division,
since they are contrary to one another. Therefore they are naturally
simultaneous. Therefore love is not the cause of hatred.

Obj. 2: Further, of two contraries, one is not the cause of the
other. But love and hatred are contraries. Therefore love is not the
cause of hatred.

Obj. 3: Further, that which follows is not the cause of that which
precedes. But hatred precedes love, seemingly: since hatred implies a
turning away from evil, whereas love implies a turning towards good.
Therefore love is not the cause of hatred.

_On the contrary,_ Augustine says (De Civ. Dei xiv, 7, 9) that all
emotio