Obj. 4:  Further, some laws are tyrannical, as the Philosopher says (Polit. iii, 6).  But a tyrant does not intend the good of his subjects, but considers only his own profit.  Therefore law does not make men good.

On the contrary, The Philosopher says (Ethic. ii, 1) that the “intention of every lawgiver is to make good citizens.”

I answer that, as stated above (Q. 90, A. 1, ad 2; AA. 3, 4), a law is nothing else than a dictate of reason in the ruler by whom his subjects are governed.  Now the virtue of any subordinate thing consists in its being well subordinated to that by which it is regulated:  thus we see that the virtue of the irascible and concupiscible faculties consists in their being obedient to reason; and accordingly “the virtue of every subject consists in his being well subjected to his ruler,” as the Philosopher says (Polit. i).  But every law aims at being obeyed by those who are subject to it.  Consequently it is evident that the proper effect of law is to lead its subjects to their proper virtue:  and since virtue is “that which makes its subject good,” it follows that the proper effect of law is to make those to whom it is given, good, either simply or in some particular respect.  For if the intention of the lawgiver is fixed on true good, which is the common good regulated according to Divine justice, it follows that the effect of the law is to make men good simply.  If, however, the intention of the lawgiver is fixed on that which is not simply good, but useful or pleasurable to himself, or in opposition to Divine justice; then the law does not make men good simply, but in respect to that particular government.  In this way good is found even in things that are bad of themselves:  thus a man is called a good robber, because he works in a way that is adapted to his end.

Reply Obj. 1:  Virtue is twofold, as explained above (Q. 63, A. 2), viz. acquired and infused.  Now the fact of being accustomed to an action contributes to both, but in different ways; for it causes the acquired virtue; while it disposes to infused virtue, and preserves and fosters it when it already exists.  And since law is given for the purpose of directing human acts; as far as human acts conduce to virtue, so far does law make men good.  Wherefore the Philosopher says in the second book of the Politics (Ethic. ii) that “lawgivers make men good by habituating them to good works.”

Reply Obj. 2:  It is not always through perfect goodness of virtue that one obeys the law, but sometimes it is through fear of punishment, and sometimes from the mere dictates of reason, which is a beginning of virtue, as stated above (Q. 63, A. 1).