Naturalism has as many meanings as it has proponents. One way to sharpen our conception of philosophical naturalism is to look at the historical movements that led to it. In particular, naturalism as it was developed in the first half of the twentieth century is an attempt to model philosophy on the natural sciences—an effort, as it were, to realise Kant’s hoped-for ‘Copernican revolution’. Peirce’s focus on the dispositions of the scientist rather than specific experimental methods or specific experimental results demonstrates his commitment to epistemic fallibilism as well as the importance he places on recognising the changing and evolving nature of science itself. Dunham et al. charge that the too-frequent reduction of idealism writ large to Berkeleyan subjective idealism has led to the common view that idealism is anti-realist. Naturalism as a philosophical movement had its official debut in the first half of the 20th century.