Natural Law

A reader asked what I meant by “natural law.” I’m with St. Thomas: the natural law is "nothing else than the rational creature's participation in the eternal law" (I-II, Q. xciv). The eternal law is God's wisdom, inasmuch as it is the directive norm of all movement and action.

Natural law theory eventually gave rise to a concept of "natural rights." This natural rights theory provided a philosophical basis for both the American and French revolutions. Thomas Jefferson used the natural law theory to justify his trinity of "inalienable rights" which were stated in the United States Declaration of Independence.

Since law must always be some dictate of reason, natural law also will be some dictate of reason. In fact, it is law discovered by human reason. Our normal and natural grasp of the natural law is effected by reason, that is, by the thinking mind, and in this service reason is sometimes called "conscience."

The "norm" of morality is the natural law as applied by conscience. We can say that the natural law is the disposition of things as known by our human reason and to which we must conform ourselves if we are to realize our proper end or "good" as human beings.

Here’s a souce: Dr. Dolhenty's Recommended Bookshelf For Natural Law Theory