Abstract: Philosophical naturalism has dominated the Western academy for well over a century. However, there is an important sense in which naturalism's status as orthodoxy is without rational foundation. Furthermore, the costs of embracing it are surprisingly high. The goal of this book is to defend these two claims, with special attention to the second. The first part of the book aims to provide a fair and historically informed characterization of naturalism. The second part argues for the striking thesis that naturalists are committed to rejecting realism about material objects, materialism, and perhaps realism about other minds. The book concludes with an examination of two alternative research programmes – intuitionism and supernaturalism – and argues that, under certain circumstances, intuitionism is self-defeating.

Keywords: constructivism, design, dualism, intuition, intuitionism, material objects, naturalism, ontology, realism, supernaturalism