Is a zombie you possible?
Does the conceivability of zombies show that consciousness is not physical?
I
Zombies are possible, so physicalism is false
We can coherently conceive a zombie world, so such a world is possible, so the physical facts do not determine the facts about consciousness.
- Best argument
- The argument has three steps. Zombies are conceivable: there is no contradiction in the idea. What is conceivable (on ideal reflection) is possible. If zombies are possible, consciousness is not entailed by physical facts, so physicalism is false. Each step is plausible, and denying the first seems to deny that we understand what consciousness is.
- Strongest objection
- Conceivability is a poor guide to possibility. Before chemistry, people could conceive of water that was not H2O; it turned out to be impossible. Our failure to see the necessary link between brain and experience may reflect our ignorance, not the absence of a link.
- The reply
- Chalmers answers with two-dimensional semantics: the water case involves conceiving of something that looks like water, not of water itself. With consciousness, how it seems is how it is, so there is no gap between appearance and reality for the analogy to exploit.
- Defended by
- David Chalmers, Robert Kirk (early)
II
Zombies are inconceivable
When we think we are imagining a zombie, we are not really imagining a being physically identical to us. A full physical duplicate would be conscious.
- Best argument
- Daniel Dennett argues that people who think they can conceive of zombies are not imagining hard enough. A real duplicate would have the same beliefs about its experiences, the same reactions, the same internal processes producing them. Once you take all of that seriously, nothing remains for the 'missing' consciousness to be.
- Strongest objection
- Most people, including many physicalists, find zombies easy to conceive. Insisting they are inconceivable seems to deny an obvious feature of how we think about consciousness.
- Defended by
- Daniel Dennett, Robert Kirk (later)
III
Conceivable but impossible
Zombies may be conceivable, but they are not possible. Consciousness is physical, though we cannot see why from the armchair.
- Best argument
- Type-B physicalists accept that there is an explanatory gap: we cannot deduce consciousness from physics. But they hold that the identity between experiences and brain states is a brute, necessary fact, like 'water is H2O', known through investigation rather than reflection. Our ability to imagine zombies reflects the special nature of our concepts of experience, not anything about the world.
- Strongest objection
- Chalmers argues that this makes the identity uniquely mysterious: in every other case, we can explain why a necessary identity holds once we know the facts. Brute necessities with no explanation are a high price.
- Defended by
- Brian Loar, David Papineau, Ned Block
Where you stand
Could a perfect physical copy of you have no inner experience?
In surveys
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For the full background, variations and open questions, read the entry: Could there be a zombie you?.