Whether Sin Has an External Cause?
Objection 1: It would seem that sin has no external cause. For sin is
a voluntary act. Now voluntary acts belong to principles that are
within us, so that they have no external cause. Therefore sin has no
external cause.
Obj. 2: Further, as nature is an internal principle, so is the will.
Now in natural things sin can be due to no other than an internal
cause; for instance, the birth of a monster is due to the corruption
of some internal principle. Therefore in the moral order, sin can
arise from no other than an internal cause. Therefore it has no
external cause.
Obj. 3: Further, if the cause is multiplied, the effect is
multiplied. Now the more numerous and weighty the external
inducements to sin are, the less is a man's inordinate act imputed
to him as a sin. Therefore nothing external is a cause of sin.
_On the contrary,_ It is written (Num. 21:16): "Are not these they,
that deceived the children of Israel by the counsel of Balaam, and
made you transgress against the Lord by the sin of Phogor?" Therefore
something external can be a cause of sin.
_I answer that,_ As stated above (A. 2), the internal cause of sin is
both the will, as completing the sinful act, and the reason, as
lacking the due rule, and the appetite, as inclining to sin.
Accordingly something external might be a cause of sin in three ways,
either by moving the will itself immediately, or by moving the
reason, or by moving the sensitive appetite. Now, as stated above (Q.
9, A. 6; Q. 10, A. 4), none can move the will inwardly save God
alone, who cannot be a cause of sin, as we shall prove further on (Q.
79, A. 1). Hence it follows that nothing external can be a cause of
sin, except by moving the reason, as a man or devil by enticing to
sin; or by moving the sensitive appetite, as certain external
sensibles move it. Yet neither does external enticement move the
reason, of necessity, in matters of action, nor do things proposed
externally, of necessity move the sensitive appetite, except perhaps
it be disposed thereto in a certain way; and even the sensitive
appetite does not, of necessity, move the reason and will. Therefore
something external can be a cause moving to sin, but not so as to be
a sufficient cause thereof: and the will alone is the sufficient
completive cause of sin being accomplished.
Reply Obj. 1: From the very fact that the external motive causes of
sin do not lead to sin sufficiently and necessarily, it follows that
it remains in our power to sin or not to sin.
Reply Obj. 2: The fact that sin has an internal cause does not
prevent its having an external cause; for nothing external is a cause
of sin, except through the medium of the internal cause, as stated.
Reply Obj. 3: If the external causes inclining to sin be multiplied,
the sinful acts are multiplied, because they incline to the sinful
act in both greater numbers and greater frequency. Nevertheless the
character of guilt is lessened, since this depends on the act being
voluntary and in our power.
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