Sound economic policy, morally upright economic judgment and action, and a stable web of economic institutions and agents are all essential for human well-being. The absence of any of these things creates crucial obstacles to the flourishing of persons, both individually and socially. A natural law theory is, in essence, a critical and reflective account of the constitutive aspects of the well-being and fulfillment of human persons and their communities, and of the requirements that human well-being place on human actions. So the project of bringing natural law theory to bear on questions of economics is entirely to the good. The natural law tradition, manifested in thinkers such as Plato, Aristotle, and St. Thomas Aquinas and his successors, has typically attended to some of the crucial concerns at the intersection of economic activity and human well-being. Natural law thinkers have addressed the nature of property and of charitable obligations, the role of money and money lending, and the context of moral principles governing relations between states in ways that continue to influence the West's common thinking. Yet insights of the natural law tradition on such matters have also become occluded as new theories, new situations, and new technologies have shaped the context in which economic choice and action take place.
The purpose of this Essay is to identify both the natural law justification for a free market--hence the Essay's concern for freedom--and the broad natural law understanding of the primary moral norm governing that market--hence the Essay's concern for equality. Both freedom and equality, properly understood, are essential to the natural law account of the market as presented by its greatest proponent, St. Thomas Aquinas. (1) Separate either from the other and the account will cease to be recognizable as genuinely belonging to the natural law tradition.
Aquinas famously provided a rather pessimistic account of the justification for private property. The goods of the earth are in one sense to be held in common: They exist for the benefit of all persons and have no particular person's name attached to them by nature. (2) Yet, if men hold and dispose of property in common, various problems will arise. Aquinas noted in particular that people will care less adequately for what they do not think of as their own. (3) Communal ownership can also lead to confusion over what should be done with the property. This uncertainty can lead to quarrels. Private property is thus justified for the purpose of procuring and dispensing of goods, but property is still common in regards to the use to which it is put. (4)
John Finnis has offered an important addendum to this pessimistic justification. Private property contributes to the freedom and autonomy of individuals, which benefits them in the task of becoming self-constituting, flourishing human beings. (5) In the natural law tradition, freedom is not treated as good in itself; it becomes good, however, because it allows human beings to participate actively in shaping their own lives. (6) As Aquinas wrote, practical reason is our very participation in the eternal law: God chooses to guide us towards our perfection not by instilling in us principles of direction that determine our actions, but by allowing us, through our own knowledge of those principles, to direct ourselves towards our fulfillment and to decide for ourselves whether or not to act. (7) In this "participated theonomy," we are active cooperators with God in shaping our lives in accordance with His plan. (8) We can thus identify God's call to each individual to share in that self-shaping project as that person's "vocation." (9)
Such self-shaping is greatly enhanced by the institution of private property. Private ownership allows agents to decide how they will procure and dispose of property in accordance with, and in service of, their vocation in a way that would not otherwise be possible. …