We next have to consider the exterior principles of acts.  Now the exterior principle that inclines us toward evil is the devil, whose temptations were discussed in the first part (ST 1, question 114).  On the other hand, the exterior principle that moves us toward the good is God, who both instructs us with law and assists us with grace.  Hence, we must first discuss law (questions 90-108) and then grace (questions 109‑114).

On the topic of law, we must first consider law itself in general (questions 90‑92) and then the parts of law (questions 93‑108).

Now there are three things to consider about law in general:  first, the essence of law (question 90); second, the different kinds of law (question 91); and, third, the effects of law (question 92).

On the first topic there are four questions:  (1) Is law something that belongs to reason?  (2) What is the end or purpose (finis) of law? (3) What is the cause of law?  (4) What about the promulgation of law?