We have now to consider the extrinsic principles of acts. Now the extrinsic principle inclining to evil is the devil, of whose temptations we have spoken in the FP, Q. But the extrinsic principle moving to good is God, Who both instructs us by means of His Law, and assists us by His Grace: wherefore in the first place we must speak of law; in the second place, of grace.
Concerning law, we must consider: (1) Law itself in general; (2) its parts. Concerning law in general three points offer themselves for our consideration: (1) Its essence; (2) The different kinds of law; (3) The effects of law.
Under the first head there are four points of inquiry:
(1) Whether law is something pertaining to reason?
(2) Concerning the end of law;
(3) Its cause;
(4) The promulgation of law.