Theodicy

extended to all the laws of the Decalogue, if the actions they command are in their nature divested of all goodness to the same degree as the actions they forbid.'

181. To say that God, having resolved to create man just as he is, could not but have required of him piety, sobriety, justice and chastity, because it is impossible that the disorders capable of overthrowing or disturbing his work can please him, that is to revert in effect to the common opinion. Virtues are virtues only because they serve perfection or prevent the imperfection of those who are virtuous, or even of those who have to do with them. And they have that power by their nature and by the nature of rational creatures, before God decrees to create them. To hold a different opinion would be as if someone were to say that the rules of proportion and harmony are arbitrary with regard to musicians because they occur in music only when one has resolved to sing or to play some instrument. But that is exactly what is meant by being essential to good music: for those rules belong to it already in the ideal state, even when none yet thinks of singing, since it is known that they must of necessity belong to it as soon as one shall sing. In the same way virtues belong to the ideal state of the rational creature before God decrees to create it; and it is for that very reason we maintain that virtues are good by their nature.