naturalism the twofold view that (1) everything is composed of natural entities – those studied in the sciences (on some versions, the natural sciences) – whose properties determine all the properties of things, persons included (abstracta like possibilia and mathematical objects, if they exist, being constructed of such abstract entities as the sciences allow); and (2) acceptable methods of justification and explanation are continuous, in some sense, with those in science. Clause (1) is metaphysical or ontological, clause (2) methodological and/or epistemological. Often naturalism is formulated only for a specific subject matter or domain. Thus ethical naturalism holds that moral properties are equivalent to or at least determined by certain natural properties, so that moral judgments either form a subclass of, or are (non-reductively) determined by the factual or descriptive judgments, and the appropriate methods of moral justification and explanation are continuous with those in science. Aristotle and Spinoza sometimes are counted among the ancestors of naturalism, as are Democritus, Epicurus, Lucretius, and Hobbes. But the major impetus to naturalism in the last two centuries comes from advances in science and the growing explanatory power they signify. By the 1850s, the synthesis of urea, reflections on the conservation of energy, work on ‘animal electricity,’ and discoveries in physiology suggested to Feuerbach, L. Buchner, and others that all aspects of human beings are explainable in purely natural terms. Darwin’s theory had even greater impact, and by the end of the nineteenth century naturalist philosophies were making inroads where idealism once reigned unchallenged. Naturalism’s ranks now included H. Spencer, J. Tyndall, T. H. Huxley, W. K. Clifford, and E. Haeckel. Early in the twentieth century, Santayana’s naturalism strongly influenced a number of American philosophers, as did Dewey’s. Still other versions of naturalism flourished in America in the 1930s and 1940s, including those of R. W. Sellars and M. Cohen. Today most American and other philosophers of mind are naturalists of some stripe, largely because of what they see as the lessons of continuing scientific advances, some of them spectacular, particularly in the brain sciences.
Nonetheless, twentieth-century philosophy has been largely anti-naturalist. Both phenomenology in the Husserlian tradition and analytic philosophy in the Fregean tradition, together with their descendants, have been united in rejecting psychologism, a species of naturalism according to which empirical discoveries about mental processes are crucial for understanding the nature of knowledge, language, and logic. In order to defend the autonomy of philosophy against inroads from descriptive science, many philosophers have tried to turn the tables by arguing for the priority of philosophy over science, hence over any of its alleged naturalist implications. Many continue to do so, often on the ground that philosophy alone can illuminate the normativity and intentionality involved in knowledge, language, and logic; or on the ground that philosophy can evaluate the normative and regulative presuppositions of scientific practice which science itself is either blind to or unequipped to analyze; or on the ground that phi- losophy understands how the language of science can no more be used to get outside itself than any other, hence can no more be known to be in touch with the world and ourselves than any other; or on the ground that would-be justifications of fundamental method, naturalist method certainly included, are necessarily circular because they must employ the very method at issue.
Naturalists may reply by arguing that naturalism’s methodological clause (2) entails the opposite of dogmatism, requiring as it does an uncompromising fallibilism about philosophical matters that is continuous with the open, selfcritical spirit of science. If evidence were to accumulate against naturalism’s metaphysical clause (1), (1) would have to be revised or rejected, and there is no a priori reason such evidence could in principle never be found; indeed many naturalists reject the a priori altogether. Likewise, (2) itself might have to be revised or even rejected in light of adverse argument, so that in this respect (2) is self-referentially consistent. Until then, (2)’s having survived rigorous criticism to date is justification enough, as is the case with hypotheses in science, which often are deployed without circularity in the course of their own evaluation, whether positive or negative (H. I. Brown, ‘Circular Justifications,’ 1994). So too can language be used without circularity in expressing hypotheses about the relations between language and the prelinguistic world (as illustrated by R. Millikan’s Language, Thought and Other Biological Categories, 1984; cf. Post, ‘Epistemology,’ 1996). As for normativity and intentionality, naturalism does not entail materialism or physicalism, according to which everything is composed of the entities or processes studied in physics, and the properties of these basic physical affairs determine all the properties of things (as in Quine). Some naturalists deny this, holding that more things than are dreamt of in physics are required to account for normativity and intentionality – and consciousness. Nor need naturalism be reductive, in the sense of equating every property with some natural property. Indeed many physicalists themselves explain how the physical, hence natural, properties of things might determine other, non-natural properties without being equivalent to them (G. Hellman, T. Horgan, D. Lewis; see J. Post, The Faces of Existence, 1987). Often the determining physical properties are not all properties of the thing x that has the non-natural properties, but include properties of items separated from x in space and time or in some cases bearing no physical relation to x that does any work in determining x’s properties (Post, ‘ ‘Global’ Supervenient Determination: Too Permissive?’ 1995). Thus naturalism allows a high degree of holism and historicity, which opens the way for a non-reductive naturalist account of intentionality and normativity, such as Millikan’s, that is immune to the usual objections, which are mostly objections to reduction. The alternative psychosemantic theories of Dretske and Fodor, being largely reductive, remain vulnerable to such objections. In these and other ways non-reductive naturalism attempts to combine a monism of entities – the natural ones of which everything is composed – with a pluralism of properties, many of them irreducible or emergent. Not everything is nothing but a natural thing, nor need naturalism accord totalizing primacy to the natural face of existence. Indeed, some naturalists regard the universe as having religious and moral dimensions that enjoy a crucial kind of primacy; and some offer theologies that are more traditionally theist (as do H. N. Wieman, C. Hardwick, J. Post). So far from exhibiting ‘reptilian indifference’ to humans and their fate, the universe can be an enchanted place of belonging. See also A PRIORI , EMERGENCE , HOLISM, INTENTIONALITY, METAPHYSICS , PHILOSOPHY OF MIND , PHYSICALISM , PROPERTY, PSYCHOL – OGISM , SUPERVENIENCE , THEOLOGICAL NATU – RALIS. J.F.P.