Faith, reason and natural law

Often when speaking about natural law, it is common to assume that a belief in the law of nature as a moral force (as opposed to natural physical laws like gravity) goes hand in hand with religious belief.  It is certainly true that religious faith, at least in the West, has served as the foundation for many natural law thinkers -- like Thomas Aquinas, Richard Hooker, and Hugo Grotius -- natural law itself is not grounded on revelation, but rather on reason reflecting on the natural order. The principles of natural law don't violate the moral norms found, for example, in the Bible, but they aren't dependent on the Bible or other religious texts for its authority. Rather, natural law proceeds from a rational reflection on nature and the purpose of human life.

At the risk of Tom chastising me for Catholicizing the blog, I would like to offer as proof of this some of the insights of one of the most profound natural law theorists of the 19th and early 20th centuries, Pope Leo XIII, on private property. His approach is based on an appeal to reason reflecting on natural human relationships both with things and with other people. Leo's approach is a classic example of natural law reasoning:

The fact that God gave the whole human race the earth to use and enjoy cannot indeed in any manner serve as an objection against private possessions. For God is said to have given the earth to mankind in common, not because He intended indiscriminate ownership of it by all, but because He assigned no part to anyone in ownership, leaving the limits of private possessions to be fixed by the industry of men and the institutions of peoples. Yet, however the earth may be apportioned among private owners, it does not cease to serve the common interest of all, inasmuch as no living being is sustained except by what the fields bring forth. Those who lack resources supply labor, so that it can be truly affirmed that the entire scheme of securing a livelihood consists in the labor which a person expends either on his own land or in some working occupation, the compensation for which is drawn ultimately from no other source than from the varied products of the earth and is exchanged for them. For this reason it also follows that private possessions are clearly in accord with nature. The earth indeed produces in great abundance the things to preserve and, especially, to perfect life, but of itself it could not produce them without human cultivation and care. Moreover, since man expends his mental energy and his bodily strength in procuring the goods of nature, by this very act he appropriates that part of physical nature to himself which he has cultivated. On it he leaves impressed, as it were, a kind of image of his person, so that it must be altogether just that he should possess that part as his very own and that no one in any way should be permitted to violate his right.

Pope Leo XIII, Rerum Novarum (1891). The only theological principle that Leo grounds his analysis upon is the role of God as creator. Once that is established, the rest of Leo's argument flows along rational principles based on the the natural of property, labor and the needs of the human person to work and activity. Leo's approach here is one that people of faith would be wise to emulate when venturing in public debate. Not to deny their faith or its importance in their lives, but to appeal to common reason reflecting on nature to make their point, not out of a crass desire to practice political rhetoric, but out of a desire to accurately present not God's revelation alone, but the law of nature.