Social Philosophy and Policy

Research Article


Scott MacDonalda1

a1 Philosophy, Cornell University


Aquinas argues that practical reasoning requires foundations: first practical principles (ultimate ends) grasped by us per se from which deliberation proceeds. Contrary to the thesis of an important paper of Terence Irwin's, I deny that Aquinas advances two inconsistent conceptions of the scope of deliberation and, correspondingly, two inconsistent accounts of the content of the first practical principles presupposed by deliberation. On my account, Aquinas consistently takes first practical principles to be highly abstract, general, or formal ends, ends subject to specification and determination by a process of reasoning. Aquinas therefore gives deliberation wide scope, allowing (indeed, requiring) it not only to settle for us the things that are for the sake of our ends but also to engage in determining in important respects what our ends are. Accordingly, I conclude that Aquinas's foundations in ethics are “thin.” Our natural grasp of first practical principles gives us very little in the way substantive ethical principles.


I read earlier versions of this paper to the philosophy departments at Purdue University, UCLA, and Texas A&M University, and at a conference at the University of Toronto. I am grateful to the audiences on those occasions for stimulating discussion. I am grateful, too, for helpful comments from the other contributors to this volume, and its editors.