Bas van Fraassen notes how there has been a rehabilitation of metaphysics in analytic philosophy of science in recent years. This is peculiar because analytic philosophy since Russell and Wittgenstein had been rigorously empiricist. So why the change of heart? Perhaps in part it is simply one of those periodic changes of fashion to be expected in academic philosophy. But in part it seems to me driven by the normative notion that philosophy of science should be doing something to help establish a scientific worldview in the face of public challenges to the teaching of evolution. Thus enters Naturalism. Naturalism is the metaphysical view that ‘Nature is all there is’. It is quite sad to see philosophers having to go down this road again toward the empty tautologies of metaphysics. But we might feel sympathy. Perhaps they feel the need to negate the persisting religious beliefs in a Beyond Nature, which seem to threaten science. This debate offers us an opportunity to learn what Kant and Hegel each recognized as the dialectical character of reason itself in its attempt to understand reality. For Kant, in the Transcendental Dialectic of the Critique of Pure Reason, he shows the utter futility of attempting to establish the truth of any transcendent proposition empty of any specific, empirical, experiential content, like ‘Nature is all there is’. Kant shows that when reason attempts to construct an argument for such a non-empirical proposition, there is necessarily an equal possibility to construct a directly opposing, contrary argument. Hegel’s whole philosophy consists in the negation of this self-negating character of speculative reason discovered by Kant insofar as Hegel sees this transcendental negativity of reason as the very freedom of thought or reason as such learning to recognize its own freedom from given-ness in philosophy. Thus the dialectician should help the naive metaphysician who holds ‘Nature is all there is’ to see how he has already stepped over the line toward thinking the negation of this proposition, i.e., he needs to be shown that his concept is incoherent insofar as “Nature” as he uses it could not even have any meaning, would be utterly unintelligible, if one could not conceive some kind of contrasting category. If “Nature” means “determined” then non-determined or free must be conceivable. If “Nature” means “material” then there must necessarily be some intelligible sense to ‘non-materiality’ in contrast. These Dialectics of thought as Hegel conceives do not necessarily prove anything about the nature of reality — Hegel is not a retrograde or naive pre-Kantian metaphysician — rather, what Hegel is arguing is that this process is how our experience as reasoning beings unfolds the basic categories of human thought, the categories in which the world is intelligible to us. Hegel’s argument is thus not metaphysical but phenomenological. But this is different from Husserl’s and Heidegger’s existential phenomenology. Hegel’s sense of “phenomenology” puts an emphasis on the “ology” — there being a dialectical logos or logic of concepts that Hegel argues unfolds from the experience of reason, which we simply cannot avoid once we begin seriously to reason in a speculative manner. And none of this is dogmatic or old-fashioned metaphysics, reasoning by deduction from first principles, because Hegel is just saying that whenever we freely think philosophically, we will necessarily generate opposing concepts like these.