Natural law by: St. Thomas of Aquinas
If a rock falls from a cliff and hits us on the head we do not punish it. We do not blame the pig for being greedy or rebuke the monkey for its cruelty. It is their nature to be that way. It is the law of their being. But when a human being strikes us, or is greedy or cruel, we blame him and say he should act differently. For the law of man’s nature is not the same as the law of a stone or animal. The stone and the animal have a built-in drive toward the goal proper to their natures. Man’s nature is open, he can determine his own goal, and he is free.
Man’s freedom is not a blind freedom. He is given the power of reason by means of which he can discern the over-all order of things to which he should conform himself. The over-all order of things is the law of the universe, the law by which God regulates all creation. Man’s law is to put himself through his free actions in conformity with what reason tells him is his true end. This is what is meant by the natural or moral law: man’s rational and free participation n the over-all order established by God. It may be defined as the eternal law or disposition of things as known by reason, to which man must conform himself if he is to realize his end. The natural law, then, is not made by man, but is based on the structure of reality itself. It is therefore, the same for all men and all times, an unchanging rule or pattern which is there for us to discover, and by means of which we can rationally guide ourselves to our goal.