• evolutionary ethics;
  • natural law;
  • sociobiology

Abstract. Traditional Darwinian theory presents two difficulties for Thomistic natural-law morality: relativism and essentialism. The sociobiology of E. O. Wilson seems to refute the idea of evolutionary relativism. Larry Arnhart has argued that Wilson's views on sociobiology can provide a scientific framework for Thomistic natural-law theory. However, in his attempt to reconcile Aquinas's views with Wilson's sociobiology, Arnhart fails to address a critical feature of Aquinas's ethics: the role of rational goods in natural law. Arnhart limits Aquinas's understanding of rationality to the Humean notion of economic rationality–that “reason is and ought to be the slave of the passions.” On Aquinas's view, rationality discovers goods that transcend the merely biological, viz., the pursuit of truth, virtue, and God. I believe that Aquinas's natural-law morality is consistent with some accounts of sociobiology but not the more ontologically reductionist versions like the one presented by Wilson and defended by Arnhart. Moreover, Aquinas's normative account of rationality is successful in refuting the challenges of evolutionary relativism as well as the reductionism found in most sociobiological approaches to ethics.