Geert Keil, "Naturalism", in: Dermot Moran (ed.), The Routledge Companion to Twentieth-Century Philosophy, London: Routledge 2008, Ch. 6, 254-307. https://www.routledge.com/The-Routledge-Companion-to-Twentieth-CenturyPhilosophy/author/p/book/9780415299367 NATURALISM Geert Keil 1. Introduction 2. Naturalism in the First Half of the Century 3. Three Eminent Figures 3.1 Husserl 3.2 Wittgenstein 3.3 Quine 4. The Nature of Naturalism 5. A Classification of Naturalisms 5.1 Metaphysical Naturalism 5.2 Methodological, or Scientific, Naturalism 5.2.1 Naturalism with a Leading Science: Physicalism and Biologism 5.2.2 Naturalism without a Leading Science 5.3. Analytic, or Semantic, Naturalism 6. Three Fields of Naturalisation 6.1 Naturalising Epistemology 6.2 Naturalising Intentionality 6.3 Naturalising Normativity 7. Naturalism and Human Nature 8. Scientific naturalism quo vadis? 8.1 Scientia mensura and the Disunity of the Special Sciences 8.2 The Business of Philosophy 6 NATURALISM Geert Keil Introduction "We are all naturalists now," declared Roy Wood Sellars (1880–1973) in 1922.1 A bold assertion then, it had come closer to the truth by the end of the century. During the course of the twentieth century, "naturalism" seems to have become a synonym for a respectable philosophical methodology. On the other hand, there are a number of distinguished philosophers who advise against paying too much attention to what they view as a long series of unsuccessful naturalistic endeavors. As Peter Geach (1916– ) has written: When we hear of some new attempt to explain reasoning or language or choice naturalistically, we ought to react as if we were told someone had squared the circle or proved √2 to be rational: only the mildest curiosity is in order – how well has the fallacy been concealed?2 This clash of opinions is remarkable. For Geach, it goes without saying that the series of naturalistic approaches is a series of failures, whereas Sellars takes it for granted that we are all naturalists now. It appears that the parties are not talking about the same thing. Sellars described naturalism as "less a philosophical system than a recognition of the impressive implications of the physical and biological sciences."3 This characterization is typical for naturalists from the first half of the century. John Dewey (1859–1952) described a naturalist as "one who has respect for the conclusions of natural science."4 If this kind of respect suffices to be converted to naturalism, then one can easily accept Sellars's view. It seems silly to deny or belittle the unprecedented success of the natural sciences since the Enlightenment. Or, in the words of Bouwsma, "Who then would not accept scientific method, and prefer to go to Babylon by candlelight? Scientific method is successful."5 If the only alternatives to naturalism are obscurantism, superstition, and supernaturalism, then naturalism seems to be the only game in town in our scientific culture. Although there still exist enclaves of religiously motivated supernaturalism, particularly in the United States, naturalism has become the most forceful metaphilosophical trend of the twentieth century. NATUR ALISM 255 When Geach takes any "new attempt to explain reasoning or language or choice naturalistically" to be doomed to failure, he has more specific and demanding tasks in mind. Sellars and Dewey give general vindications for the natural sciences, whereas Geach refers to specific projects of naturalization. Now, having respect for the natural sciences and their methods does not yet guarantee the success of specific naturalistic projects. When it comes to these projects, naturalism does not compete with obscurantism and supernaturalism, but rather with well-established philosophical theories that purport to explain phenomena with the use of non-empirical methods. Some naturalists hold that non-empirical methods are unscientific. But if this were true, then, not only philosophy but also neither mathematics nor logic could contribute to our scientific picture of the world. The attractiveness of philosophical naturalism crucially hinges on the available alternatives. As long as naturalists confine themselves to selling their position as a bulwark against irrationality, obscurantism, and superstition, they insinuate that any kind of philosophy not committed to naturalism must be obscurantist.6 So let us take a step back. The Oxford English Dictionary defines a naturalist as "one who studies natural, in contrast to spiritual, things," or as "one who studies, or is versed in, natural science."7 This non-philosophical meaning can be traced back to the medieval Latin expression naturalista. Secondly, a naturalist is someone who believes in philosophical naturalism, which is characterized by the OED as "a view of the world, and of man's relation to it, in which only the operation of natural (as opposed to supernatural or spiritual) laws and forces is admitted or assumed." Finally, in literary theory and the history of art, "naturalism" is a term for a certain style or epoch. Zola was a naturalist in the third sense of the word, Quine in the second, and Darwin in the first. Only naturalism in the second sense is a philosophical position. It is this second sense that this chapter addresses. Naturalism in the first half of the century As a philosophical trend, naturalism has played a prominent role since the late nineteenth century. Of course, the term is older. Christian apologetics from the seventeenth century used it in a pejorative sense. Naturalists were labeled with the epithets "blasphemous" and "atheistic," where a naturalist was simply someone who refused Christian supernaturalism. As quoted above from the OED, naturalists aimed to explain all phenomena with "the operation of natural (as opposed to supernatural or spiritual) laws and forces." Philosophical naturalism in the present sense of the word has been characterized thus: "The closest thing to a common core of meaning is probably the view that the methods of natural science provide the only avenue to truth."8 Understood in this sense, the term has been in use on a larger scale since the late nineteenth century. Unquestionably, Hobbes and Hume would today call themselves "naturalists," and so would Holbach and LaMettrie. We have to keep in mind, however, that the geography of those debates was described in different terms. Throughout the nineteenth century, other -isms covered what is subsumed under "naturalism" today: materialism, mechanism, positivism, empiricism, and monism.