Abstract

When Saint Thomas Aquinas makes claims such as “that which is not just seems to be no law at all” it is a bit difficult to discern what he means. Some think that Aquinas is defending what is now called the Strong Natural Law Thesis: for all X, X is a law only if X is just. Others think that Aquinas is defending what is now called the Weak Natural Law Thesis: for all X, X is a non-defective law only if X is just. In this paper, focusing on Aquinas’s metaphysics, I argue that both of these interpretations are mistaken. Aquinas is primarily defending what we can call The Metaphysical Natural Law Thesis: since being and goodness are convertible, legal validity comes in degrees—and this entails that the justice of a law literally increases the amount of being a law possesses, while the injustice of a law literally decreases the amount of being a law possesses. On this interpretation, then, the injustice of a law entails an ontological attenuation of the law without entailing an ontological annihilation of the law