A note from Australia. Thomas Aquinas writes in the Summa that “the divine law commands certain things because they are good, and forbids others because they are evil -- while others are good because they are prescribed, and others evil because they are forbidden.”
I’m puzzled about this because I don’t want to fall into thinking that law is nothing more than a decree by someone more powerful, with no necessary relation to natural law, reason, or goodness.
The Angelic Doctor is galaxies away from suggesting that divine laws have no necessary relation to natural law, reason, or goodness. God is Law, Reason, and Good Himself, in person. So let’s take apart St. Thomas’s statement.
When he says that some acts are commanded because they are good and forbidden because they are evil, he is thinking of the acts commanded and forbidden by the moral precepts summarized by the Decalogue, for example “Honor your parents” and “Do not steal.” These express the very intention of God’s justice, and each of them is a precept of natural law.
Now to understand what he means when he says some acts are good because they are commanded and evil because they are forbidden, consider an analogy from the laws we humans enact. It isn’t intrinsically evil to drive on the left. On the other hand, it is intrinsically evil to neglect the safety of our neighbors on the roads. Now we might provide for their safety by requiring everyone to drive on the right, or by requiring everyone to drive on the left, but we can’t have it both ways, or we will collide with each other. Public authority has to make a choice, so it does. Now it is evil to drive on the left (in my country, anyway), just because this is how public authority has settled the matter. Driving on the right is now good because it is commanded. This doesn’t mean that the rule has no relation to natural law, reason, or goodness. On the contrary, the rule makes it possible to care for the safety of our neighbors, because now we aren’t working at cross purposes. So the thing that is good because it is commanded -- is commanded for the sake of the thing that is commanded because it is good. (Say that three times quickly.)
With divine law, matters stand just the same. Consider some of the precepts of the Old Testament. That the Hebrew people were to worship God together was commanded because it is good, but that they should do so on the seventh day was good because it was commanded. That they were to provide for the poor was commanded because it is good, but that they should do so by giving them the right to glean what the harvesters have overlooked was good because it was commanded. That they were to uphold justice was commanded because it was good, but that they should do so by requiring the thief to pay back four sheep for each sheep that he had stolen was good because it was commanded.
These details are called determinations of the basic moral precepts, which means that they fill in the blanks that the basic moral precepts leave unspecified. Only by filling them in can the purposes of the basic moral precepts be fulfilled.