Abstract

Contemporary debates on the nature and scope of practical reason are often framed in terms of the viewpoints of a few major figures in the history of philosophy. Whereas advocates of skeptical or procedural approaches to practical reason generally seek historical support from Hume, defenders of more substantive conceptions of practical rationality tend to draw inspiration from Aristotle or Kant. This paper argues that it is in fact the work of Aquinas which offers the best material for a defense of a substantive conception of practical rationality. After outlining the distinction between procedural and substantive conceptions, the author turns to Christine M. Korsgaard’s rearticulation of a Kantian viewpoint on practical reason. The advocate of a Kantian framework, he argues, is less well equipped than the defender of the Thomistic conception to meet necessary constraints on a substantive account. The paper closes with a discussion of the way contemporary versions of natural law theory can meet these constraints.