Abstract

Finnis claims that his theory proceeds from seven basic principles of practical reason that are self-evidently true. While much has been written about the claim of self-evidence, this article considers it in relation to the rigorous claims of logic and mathematics. It argues that when considered in this light, Finnis equivocates in his use of the concept of self-evidence between the realist Thomistic conception and a purely formal, modern symbolic conception. Given his respect for the modern positivist separation of fact and value, the realism of the Thomistic conception cannot be the foundation for the natural law as Finnis would reconstruct it. Nor can the purely formal modern conception of self-evidence provide a foundation for practical reason. This raises some doubt as to whether there can be self-evident principles of practical reason as Finnis suggests. The article contributes to the analysis of the Finnis reconstruction of the natural law by providing a rigorous analysis of his claim for self-evidence. It frames this analysis historically, suggesting the roles that certainty and mystery play in the apprehension of moral meaning.