In this article I trace some of the main tenets of the struggle between nominalism and realism as identified by John Deely in his Four ages of understanding. The aim is to assess Deely’s claim that the Age of Modernity was nominalist and that the coming age, the Age of Postmodernism — which he portrays as a renaissance of the late middle ages and as starting with Peirce — is realist. After a general overview of how Peirce interpreted the nominalist-realist (...) controversy, Deely gives special attention to Thomas Aquinas’s On being and essence and the realism it entails. A subsequent discussion of the Modern Period shows that the issue of nominalism and realism is very much tied up with di¤erent conceptions of the intellect. Deely credits the theory of evolution with bringing us a conception of the intellect that is closer to that of the Middle Ages and that opens the way for a truly realistic ‘‘fourth age’’ of the understanding. (shrink)