Some materialists believe that physics is rich enough to bridge Levine's Explanatory Gap1, while others believe that it is not. Here I promote an intermediate position holding that physics is rich enough to explain why this gap seems more intractable than similar inter-theoretic explanatory gaps, without providing a full-blown “physical” explanation of consciousness. At a minimum, such an approach needs to explore the prospects of empirical discoveries that can diminish the power of anti-physicalist arguments like Chalmers's “conceivability argument”2 and Jackson's (...) “knowledge argument.” While this is not an easy task, recent advances in the physics of spacetime and information convince us that these prospects are not poor. The empirical bent of this approach suggests framing it as a naturalist theory of mind seeking to situate or make room for consciousness within our great naturalist system, but the reliance of this approach on recent (re)conceptions of time and information pulls the carpet out from under essential concepts like concreteness and causation, thus demanding a radically reconfigured naturalism, or neo-naturalism. The question that will frame this discussion is, “What could possibly count as an empirical fact that can help naturalize consciousness?”. (shrink)

This paper is an enquiry into the logical, metaphysical, and physical possibility of time travel understood in the sense of the existence of closed worldlines that can be traced out by physical objects. We argue that none of the purported paradoxes rule out time travel either on grounds of logic or metaphysics. More relevantly, modern spacetime theories such as general relativity seem to permit models that feature closed worldlines. We discuss, in the context of Gödel's infamous argument for the ideality (...) of time based on his eponymous spacetime, what this apparent physical possibility of time travel means. Furthermore, we review the recent literature on so-called time machines, i.e., of devices that produce closed worldlines where none would have existed otherwise. Finally, we investigate what the implications of the quantum behaviour of matter for the possibility of time travel might be and explicate in what sense time travel might be possible according to leading contenders for full quantum theories of gravity such as string theory and loop quantum gravity. (shrink)

This chapter contains sections titled: Highlights of Past Literature Current Work Future Work.

I discuss the formal implementation, interpretation, and justification of likelihood attributions in cosmology. I show that likelihood arguments in cosmology suffer from significant conceptual and formal problems that undermine their applicability in this context.

Four empirically equivalent versions of general relativity, namely standard GR, Lorentz-invariant gravitational theory,and the gravitational gauge theories of the Lorentz and translation groups, are investigated in the form of a case study for theory underdetermination. The various ontological indeterminacies (both underdetermination and inscrutability of reference) inherent in gravitational theories are analyzed in a detailed comparative study. The concept of practical underdetermination is proposed, followed by a discussion of its adequacy to describe scientific progress.