Whether Good Can Be the Cause of Evil?
Objection 1: It would seem that good cannot be the cause of evil. For
it is said (Matt. 7:18): "A good tree cannot bring forth evil fruit."
Obj. 2: Further, one contrary cannot be the cause of another. But
evil is the contrary to good. Therefore good cannot be the cause of
evil.
Obj. 3: Further, a deficient effect can proceed only from a deficient
cause. But evil is a deficient effect. Therefore its cause, if it has
one, is deficient. But everything deficient is an evil. Therefore the
cause of evil can only be evil.
Obj. 4: Further, Dionysius says (Div. Nom. iv) that evil has no
cause. Therefore good is not the cause of evil.
_On the contrary,_ Augustine says (Contra Julian. i, 9): "There is no
possible source of evil except good."
_I answer that,_ It must be said that every evil in some way has a
cause. For evil is the absence of the good, which is natural and due
to a thing. But that anything fail from its natural and due
disposition can come only from some cause drawing it out of its proper
disposition. For a heavy thing is not moved upwards except by some
impelling force; nor does an agent fail in its action except from some
impediment. But only good can be a cause; because nothing can be a
cause except inasmuch as it is a being, and every being, as such, is
good.
And if we consider the special kinds of causes, we see that the
agent, the form, and the end, import some kind of perfection which
belongs to the notion of good. Even matter, as a potentiality to
good, has the nature of good. Now that good is the cause of evil by
way of the material cause was shown above (Q. 48, A. 3). For it was
shown that good is the subject of evil. But evil has no formal cause,
rather is it a privation of form; likewise, neither has it a final
cause, but rather is it a privation of order to the proper end; since
not only the end has the nature of good, but also the useful, which
is ordered to the end. Evil, however, has a cause by way of an agent,
not directly, but accidentally.
In proof of this, we must know that evil is caused in the action
otherwise than in the effect. In the action evil is caused by reason
of the defect of some principle of action, either of the principal or
the instrumental agent; thus the defect in the movement of an animal
may happen by reason of the weakness of the motive power, as in the
case of children, or by reason only of the ineptitude of the
instrument, as in the lame. On the other hand, evil is caused in a
thing, but not in the proper effect of the agent, sometimes by the
power of the agent, sometimes by reason of a defect, either of the
agent or of the matter. It is caused by reason of the power or
perfection of the agent when there necessarily follows on the form
intended by the agent the privation of another form; as, for instance,
when on the form of fire there follows the privation of the form of
air or of water. Therefore, as the more perfect the fire is in
strength, so much the more perfectly does it impress its own form, so
also the more perfectly does it corrupt the contrary. Hence that evil
and corruption befall air and water comes from the perfection of the
fire: but this is accidental; because fire does not aim at the
privation of the form of water, but at the bringing in of its own
form, though by doing this it also accidentally causes the other.
But if there is a defect in the proper effect of the fire--as, for
instance, that it fails to heat--this comes either by defect of the
action, which implies the defect of some principle, as was said above,
or by the indisposition of the matter, which does not receive the
action of the fire, the agent. But this very fact that it is a
deficient being is accidental to good to which of itself it belongs to
act. Hence it is true that evil in no way has any but an accidental
cause; and thus is good the cause of evil.
Reply Obj. 1: As Augustine says (Contra Julian. i): "The Lord calls
an evil will the evil tree, and a good will a good tree." Now, a good
will does not produce a morally bad act, since it is from the good
will itself that a moral act is judged to be good. Nevertheless the
movement itself of an evil will is caused by the rational creature,
which is good; and thus good is the cause of evil.
Reply Obj. 2: Good does not cause that evil which is contrary to
itself, but some other evil: thus the goodness of the fire causes
evil to the water, and man, good as to his nature, causes an act
morally evil. And, as explained above (Q. 19, A. 9), this is by
accident. Moreover, it does happen sometimes that one contrary causes
another by accident: for instance, the exterior surrounding cold
heats (the body) through the concentration of the inward heat.
Reply Obj. 3: Evil has a deficient cause in voluntary things
otherwise than in natural things. For the natural agent produces the
same kind of effect as it is itself, unless it is impeded by some
exterior thing; and this amounts to some defect belonging to it.
Hence evil never follows in the effect, unless some other evil
pre-exists in the agent or in the matter, as was said above. But in
voluntary things the defect of the action comes from the will
actually deficient, inasmuch as it does not actually subject itself
to its proper rule. This defect, however, is not a fault, but fault
follows upon it from the fact that the will acts with this defect.
Reply Obj. 4: Evil has no direct cause, but only an accidental cause,
as was said above.
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