[for a brief explanation of this ongoing series, as well as a full table of contents, go here]
“To be is to be the value of a variable.”
(Willard Van Orman Quine)
We have seen so far that philosophy broadly construed has a significant public relation problem, and I’ve argued that one of the root causes of this problem is its sometimes antagonistic relationship with science, mostly, but not only, fueled by some high prominent scientists who locked horns with equally prominent anti-scientistic philosophers. In this chapter we will examine the other side of the same coin: the embracing by a number of philosophers of a more positive relationship with science, to the point of either grounding philosophical work exclusively in a science-based naturalistic view of the world, or even of attempting to erase any significant differences between philosophy and science. This complex discourse is sometimes referred to as the “naturalistic turn” in modern analytic philosophy, it arguably began with the criticism of positivism led by Willard Van Orman Quine and others in the middle part of the 20th century, and it is still shaping a significant portion of the debate in metaphilosophy, the subfield of inquiry that reflects critically on the nature of philosophy itself (Joll 2010).
Two very large caveats first. To begin with, which philosophy am I talking about now? We have seen earlier that the term applies to a highly heterogeneous set of traditions, spanning different geographical areas, cultures, and time periods. To be clear — and for the reasons I highlighted in the last chapter — from now on and for the rest of the book I will employ the term “philosophy” to indicate the broadest possible conception of the sort of activity began and named by the pre-Socratics in ancient Greece, what I termed the DRA (discursive rationality and argumentation) approach. This will comprise, of course, all of the current analytic tradition, but also parts of continental philosophy, and certain aspects or traditions of “Eastern” philosophies. It will also include the work of modern and contemporary philosophers that do not fit easily within the fairly strict confines of proper analytic philosophy: both versions of Wittgenstein, for instance, at least some strains of feminist philosophy, and much more. If this sounds insufficiently precise that is — I think — a reflection of the complexity and richness of philosophical thought, not necessarily a shortcoming of my own concept of it.
Secondly, it must be admitted that venturing into a discussion of “naturalism” is perilous, for the simple reason that there is an almost endless variety of positions within that very broad umbrella, and plenty of people who feel very strongly about them. In the following, however, I will focus specifically on approaches to naturalism (and the philosophers who pursue them) that are most useful or otherwise enlightening for the general project of this book, which largely involves the relationships between science and philosophy and how they both make progress, albeit according to different conceptions of progress.
Before tackling naturalism, we need to indulge in a bit more of what is referred to as “metaphilosophy,” i.e., philosophizing about the nature of philosophy itself. We have already examined what a number of contemporary philosophers think philosophy is, and I argued that there is significantly more agreement than a superficial look would lead one to believe, certainly more than the oft-made comment that every philosopher has a (radically) different idea of what the field is about. Arguably the most famous characterizations of philosophy were those given by two of the major figures in the field during the 20th century, Alfred Whitehead and Bertrand Russell. Whitehead quipped that all (Western) philosophy is a footnote to Plato, meaning that Plato identified all the major areas of philosophical investigation; a bit more believably, Russell commented that philosophy is the sort of inquiry that can be pursued by using the methods first deployed by Plato. The fact is, discussions concerning what the proper domain and methods of philosophy are (i.e., discussions in metaphilosophy, regardless of whether explicitly conducted in a self-conscious metaphilosophical setting) have been going on since at least Socrates. Just recall his famous analogy between his trade and the role of a midwife, which conjures an image of the philosopher as a facilitator of sound thinking; or Plato’s relentless attacks against the Sophists, who thought of themselves as legitimate philosophers, but were accused of doing something much closer to what we would consider lawyering.
I think it is obvious that Whitehead was exaggerating about all philosophy being a footnote to Plato, regardless of how generous we are inclined to be toward the Greek thinker. Not only there are huge swaths of modern philosophy (most of the contemporary “philosophies of,” to which we will return in the last chapter) which were obviously inaccessible to Plato, but he (and especially Socrates) made it pretty clear that they had relatively little interest in natural philosophy, with their focus being largely on ethics, metaphysics, epistemology (to a point), and aesthetics. It was Aristotle that further broadened the field with the development of formal logic, as well as a renewed emphasis on the sort of natural philosophy that had already took off with the pre-Socratics (particularly the atomists) and that eventually became science.
A rapid survey of post-Greek philosophy shows that different philosophers have held somewhat different views of the value of their discipline (Joll 2010). Hume, for instance, wrote that “One considerable advantage that arises from Philosophy, consists in the sovereign antidote which it affords to superstition and false religion” (Of Suicide, in Hume 1748), thus echoing the ancient Epicurean quest for freeing humanity from the fears generated by religious superstition. This somewhat practical take on the value of philosophy was also evident — in very different fashions — in Hegel, who thought that philosophy is a way to help people feel at home in the world, and in Marx, who famously quipped that the point is not to interpret the world, but to change it.
With the onset of the 20th century we have the maturing of modern academic philosophy, and the development of more narrow conceptions of the nature of the discipline. The early Wittgenstein of the Tractatus thought that philosophy is essentially a logical analysis of formal language (Wittgenstein 1921), which was naturally well received by the logical positivists that were dominant just before the naturalistic turn with which we shall shortly concern ourselves. Members of the Vienna Circle went so far as promulgating a manifesto in which they explicitly reduced philosophy to logical analysis: “The task of philosophical work lies in … clarification of problems and assertions, not in the propounding of special ‘philosophical’ pronouncements. The method of this clarification is that of logical analysis” (Neurath et al. 1973 / 1996). From these bases, it was but a small step to the forceful attack on traditional metaphysics mounted by the positivists. Metaphysics was cast aside as a pseudo-discipline, and prominent continental philosophers — especially Heidegger — were dismissed as obfuscatory cranks.
I think it is fair to say that a major change in the attitude of practicing philosophers toward philosophy coincided with the diverging rejections of positivism that are perhaps best embodied by (the later) Wittgenstein and by Quine. We will examine Quine in some more detail in the next section, since he was pivotal to the naturalistic turn. The Wittgenstein of the Investigations shifted from considering an ideal logical language to exploring the structure — and consequences for philosophy — of natural language. As a result of this shift, Wittgenstein began to think that philosophical problems need to be dissolved rather than solved, since they are rooted in linguistic misinterpretations (cfr. his famous quip about letting the fly out of the fly bottle, Investigations 309), which led to his legendary confrontation with Karl Popper, who very much believed in the existence and even solvability of philosophical questions, especially in ethics (Edmonds and Eidinow 2001).
Most crucially as far as we are concerned here, the Wittgenstein of the Investigations was critical of some philosophers’ envy of science. He thought that seeking truths only and exclusively in science amounts to a greatly diminished understanding of the world. In this Wittgenstein clearly departed not just from the attitude of the Vienna Circle and the positivists in general, but also from his mentor, the quintessentially analytic philosopher Bertrand Russell. It is because of this shift between the early and late Wittgenstein that — somewhat ironically — both analytic and continental traditions can rightfully claim him as a major exponent of their approach. 
This very brief metaphilosophical survey cannot do without a quick look at the American pragmatists, who developed a significantly different outlook on what philosophy is and how it works. Recall, to begin with, their famous maxim, as articulated by Peirce (1931-58, 5, 402): “Consider what effects, which might conceivably have practical bearings, we conceive the object of our conception to have. Then, our conception of these effects is the whole of our conception of the object.” Peirce and James famously interpreted the maxim differently, the first one referring it to meaning, the latter (more controversially) to truth. Regardless, for my purposes here the pragmatists can be understood as being friendly to naturalism and science, and indeed as imposing strict limits on what counts as sound philosophy, albeit in a very different way from the positivists.
I find it even more interesting, therefore, that the most prominent — and controversial — of the “neo-pragmatists,” Richard Rorty, attempted to move pragmatism into territory that is so antithetic to science that Rorty is nowadays often counted among “continental” and even postmodern philosophers. His insistence on a rather extreme form of coherentism, wherein justification of beliefs is relativized to an individual’s understanding of the world, (Rorty
1980), eventually brought him close to the anti-science faction in the so-called “science wars” of the 1990s and beyond (see the chapter on Philosophy Itself). He even suggested “putting politics first and tailoring a philosophy to suit” (Rorty 1991, 178). But that is not the direction I am taking here. Instead, we need to sketch the contribution of arguably the major pro-naturalistic philosopher of the 20th century, Quine, to lay the basis for a broader discussion in the latter part of this chapter of what naturalism is and what it may mean to philosophy.
 The discontinuity between the early and late Wittgenstein, however, should not be overplayed. As several commentators have pointed out, for instance, both the Tractatus and the Investigations are very much concerned with the idea that a primary task of philosophy is the critique of language.
Edmonds, D. and Eidinow, J. (2001) Wittgenstein’s Poker: The Story of a Ten-Minute Argument Between Two Great Philosophers. Ecco.
Hume, D. (1748) An Enquiry Concerning Human Understanding (accessed on 8 February 2013).
Joll, N. (2010) Contemporary metaphilosophy. Internet Encyclopedia of Philosophy (accessed on 26 June 2012).
Neurath, O., Carnap, R., Hahn, H. (1973 / 1996) The Scientific Conception of the World: the Vienna Circle, in S. Sarkar (ed.) The Emergence of Logical Empiricism: from 1900 to the Vienna Circle. Garland Publishing, pp. 321–340.
Peirce, C.S. (1931–58) The Collected Papers of Charles Sanders Peirce. C. Hartshorne, P. Weiss and A. Burks (eds). Harvard University Press.
Rorty, R. (1980) Philosophy and the Mirror of Nature. Blackwell.
Rorty, R. (1991) The Priority of Democracy to Philosophy. In: Objectivity, Relativism, and Truth. Philosophical Papers, Volume 1. Cambridge University Press.
Wittgenstein, L. (1921) Tractatus Logicus-Philosophicus (accessed on 8 February 2013).