Divine law besides the
natural inclination impressed on them. Much less, therefore, should
the rational creature have a Divine law in addition to the natural
law.

_On the contrary,_ David prayed God to set His law before him, saying
(Ps. 118:33): "Set before me for a law the way of Thy justifications,
O Lord."

_I answer that,_ Besides the natural and the human law it was
necessary for the directing of human conduct to have a Divine law.
And this for four reasons. First, because it is by law that man is
directed how to perform his proper acts in view of his last end. And
indeed if man were ordained to no other end than that which is
proportionate to his natural faculty, there would be no need for man
to have any further direction of the part of his reason, besides the
natural law and human law which is derived from it. But since man is
ordained to an end of eternal happiness which is improportionate to
man's natural faculty, as stated above (Q. 5, A. 5), therefore it was
necessary that, besides the natural and the human law, man should be
directed to his end by a law given by God.

Secondly, because, on account of the uncertainty of human judgment,
especially on contingent and particular matters, different people
form different judgments on human acts; whence also different and
contrary laws result. In order, therefore, that man may know without
any doubt what he ought to do and what he ought to avoid, it was
necessary for man to be directed in his proper acts by a law given by
God, for it is certain that such a law cannot err.

Thirdly, because man can make laws in those matters of which he is
competent to judge. But man is not competent to judge of interior
movements, that are hidden, but only of exterior acts which appear:
and yet for the perfection of virtue it is necessary for man to
conduct himself aright in both kinds of acts. Consequently human law
could not sufficiently curb and direct interior acts; and it was
necessary for this purpose that a Divine law should supervene.

Fourthly, because, as Augustine says (De Lib. Arb. i, 5, 6), human
law cannot punish or forbid all evil deeds: since while aiming at
doing away with all evils, it would do away with many good things,
and would hinder the advance of the common good, which is necessary
for human intercourse. In order, therefore, that no evil might remain
unforbidden and unpunished, it was necessary for the Divine law to
supervene, whereby all sins are