t. 2]

Whether the Devil Can Induce Man to Sin, by Internal Instigations?

Objection 1: It would seem that the devil cannot induce man to sin,
by internal instigations. Because the internal movements of the soul
are vital functions. Now no vital functions can be exercised except
by an intrinsic principle, not even those of the vegetal soul, which
are the lowest of vital functions. Therefore the devil cannot
instigate man to evil through his internal movements.

Obj. 2: Further, all the internal movements arise from the external
senses according to the order of nature. Now it belongs to God alone
to do anything beside the order of nature, as was stated in the First
Part (Q. 110, A. 4). Therefore the devil cannot effect anything in
man's internal movements, except in respect of things which are
perceived by the external senses.

Obj. 3: Further, the internal acts of the soul are to understand and
to imagine. Now the devil can do nothing in connection with either of
these, because, as stated in the First Part (Q. 111, AA. 2, 3, ad 2),
the devil cannot impress species on the human intellect, nor does it
seem possible for him to produce imaginary species, since imaginary
forms, being more spiritual, are more excellent than those which are
in sensible matter, which, nevertheless, the devil is unable to
produce, as is clear from what we have said in the First Part (Q.
110, A. 2; Q. 111, AA. 2, 3, ad 2). Therefore the devil cannot
through man's internal movements induce him to sin.

_On the contrary,_ In that case, the devil would never tempt man,
unless he appeared visibly; which is evidently false.

_I answer that,_ The interior part of the soul is intellective and
sensitive; and the intellective part contains the intellect and the
will. As regards the will, we have already stated (A. 1; I, Q. 111,
A. 1) what is the devil's relation thereto. Now the intellect, of its
very nature, is moved by that which enlightens it in the knowledge of
truth, which the devil has no intention of doing in man's regard;
rather does he darken man's reason so that it may consent to sin,
which darkness is due to the imagination and sensitive appetite.
Consequently the operation of the devil seems to be confined to the
imagination and sensitive appetite, by moving either of which he can
induce man to sin. For his operation may result in presenting certain
forms to the imagination; and he is able to incite the sensitive
appetite to some passio