David Chalmers² claims that the logical possibility of ‘zombie worlds’ — worlds physically indiscernible from the actual world, but that lack consciousness — reveal that consciousness is a distinct fact, or property, in addition to the physical facts or properties.

The ‘existence’ or possibility of Zombie worlds violates the physicalist demand that consciousness logically supervene upon the physical. On the assumption that the logical supervenience of consciousness upon the physical is, indeed, a necessary entailment of physicalism, the existence of zombie worlds implies the falsity of physicalism. How do we determine the logical possibility of zombie worlds? By conceptual analysis of the concepts involved, keeping empirical facts in mind.³ Keeping our methods in mind, we can therefore articulate the argument like this:

1. i.    I can conceive of two physically indiscernible possible worlds, one of which (the actual world) includes consciousness, but the other does not.

2. ii.    If I can conceive of these worlds, then (defeasibly) these worlds are logically possible.⁴

3. iii.    If it is logically possible that there are two worlds physically indiscernible, one of which lacks consciousness, then consciousness is not a physical fact/property.

Therefore:

1. iv.    Consciousness is not a physical fact/property [non-reductivism].

Although I like the conclusion, I shall argue skeptically that alternate metaphysical assumptions undermine Chalmers’s argument. I shall argue that if we accept causal essentialism (CE) regarding physical property identity, then the worlds Chalmers conceives are not, in fact, logically possible. The intuition that these worlds are possible is a result of not keeping all our appropriate metaphysical commitments firmly in mind. Put in a less partisan way, Chalmers’s zombie worlds are only genuine possibilities for Humeans regarding laws of nature and property identity. I shall argue that if we reject a Humean approach to laws and properties, accepting modal or causal essentialism, then we cannot accept the genuine possibility of zombie worlds.⁵

Properly conceiving the physical is as important as properly conceiving the phenomenal. Here the emphasis is on the physical. Current and popular views regarding the nature of physical concepts and properties as ‘functionalizable,’ accepted by a wide variety of philosophers, can be explained if causal essentialism is true. Causal essentialism, therefore, offers a plausible conception of the physical, yet causal essentialism causes trouble for nonreductivists who appeal to the logical possibility of zombies⁶.

In section one I introduce causal essentialism and its defenders, along with the zombie argument. I note, very briefly, some of the advantages causal essentialism has over Humean alternatives. But the reader looking for a thorough defense of causal essentialism will be disappointed. Rather, I mention some of the advantages of the theory and I offer some new considerations for favoring the theory, but I leave a full defense to others.⁷ In section two I discuss how causal essentialism can offer us a natural account for why physical property concepts seem to be causal-role or functional concepts, as Kim and Chalmers claim.⁸ I argue that Chalmers’s comments regarding complete explanations of physical properties are well accounted for by causal essentialism. Thus I am urging that causal essentialism regarding the physical is a natural metaphysical view for many, dualists and materialists alike. In section three I return to the incompatibility of zombie worlds with causal essentialism and in section four I turn to a number of objections and clarifications and finally, in section five, I briefly discuss the relationship between essentialism and dualism. Although causal essentialism deprives the dualist of the zombie possibilities, causal essentialism itself is consistent with at least one possible, although unlikely, nonreductivist view about phenomenal properties.

Whether we should accept causal essentialism depends on that view’s success at explaining other metaphysical puzzles and whether we can in all good intellectual conscience accept its consequences. CE is part and parcel of a general...