Natural Law and the Naturalistic Fallacy

Abstract

The central doctrine of the Natural Law Tradition is the Overlap Thesis—the claim that there is a necessary connection between law and morality, and that the issue of what law is cannot be separated from the issue of what law ought to be. Classical natural lawyers such as Cicero, St. Augustine, St. Thomas Aquinas, and even Common Law natural lawyers such as Sir William Blackstone invoked this thesis to illustrate how moral judgments about law could be derived from an objective moral order.

The tradition, however, was challenged by a powerful argument known as Hume’s Fork, otherwise known as the Naturalistic Fallacy, which denies that moral propositions can be deduced from purely factual premises because they belong to different logical categories. For centuries thereafter, legal philosophers doubted whether the normative force of law could be derived from morality. This article examines four solutions offered by contemporary natural lawyers to address the Naturalistic Fallacy: Lon Fuller’s Procedural Natural Law, John Finnis’ Neothomist Natural Law, Michael Moore’s Moral Realism, and Ronald Dworkin’s Constructive Natural Law. It shall be argued that although their theories have greatly improved upon those of their predecessors, each suffers various defects that render them inadequate as solutions.