Nevertheless it is referred to sin by an extrinsic principle, viz.

But such an operation does not come from an extrinsic principle.

Both of these explanations are false; for vital functions such as feeling, nourishment, and growth cannot be from an extrinsic principle.

Now the extrinsic principle inclining to evil is the devil, of whose temptations we have spoken in the First Part (Q.

We have now to consider the extrinsic principles of acts.

(6) Whether the will is moved by God alone as by an extrinsic principle?

(4) Whether it is moved by an extrinsic principle?