- David Chalmers claims that the logical possibility of 'zombie worlds' – worlds physically indiscernible from the actual world, but that lack consciousness – reveals 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 supervene1 upon the physical. On the assumption that the logical supervenience2 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.
- Keeping our methods in mind, we can therefore articulate the argument like this:-
- I can conceive of two physically indiscernible possible worlds, one of which (the actual world) includes consciousness, but the other does not.
- If I can conceive of these worlds, then (defeasibly) these worlds are logically possible.
- 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.
- 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.
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