Could there be a zombie you?
Imagine a being physically identical to you, atom for atom, who acts exactly as you do but feels nothing. If that is even possible, consciousness is something extra.
- Reading time
- 4 min
- Difficulty
- Deep
- Branch
- Mind
- First posed
- Robert Kirk, 1974; developed by David Chalmers, 1996
The setup
Not the shambling movie kind. A philosophical zombie is a being exactly like you in every physical respect. It has your brain, down to the last synapse. It walks and talks like you. If you pinch it, it says 'ouch' and pulls away. It even says, sincerely, 'I am conscious, and my experience of red is vivid and rich.'
But there is nothing it is like to be the zombie. Inside, all is dark. Its 'ouch' is a mechanism, not a pain. It processes light but sees nothing; it reports emotions but feels none.
No one claims zombies exist. The question is whether they are possible, in the broadest sense: is there a coherent world, with the same physical laws and facts as ours, in which some or all creatures like us are zombies? David Chalmers argues that zombies are at least conceivable, and that if they are possible, then the physical facts do not fix the facts about consciousness. Consciousness would then be something over and above the physical.
Why it matters
The zombie argument is one of the most discussed arguments against physicalism. It sharpens the hard problem into a precise question: is the connection between brain processes and experience necessary, like the connection between H2O and water, or contingent, something that could have been otherwise?
It also raises an uncomfortable question about knowledge of other minds. If zombies are conceivable, how do you know that the people around you are not zombies? And how do you know you are not one?
Key terms
- Philosophical zombieA hypothetical being physically identical to a person, behaving exactly the same, but with no conscious experience at all.
- PhysicalismThe view that everything that exists is physical, or is fixed by the physical facts.
- Conceivability argumentAn argument from the claim that something can be coherently imagined to the claim that it is possible. Zombie arguments against physicalism depend on it.
- SupervenienceOne set of facts supervenes on another if there can be no difference in the first without a difference in the second.
- EpiphenomenalismThe view that mental states are caused by physical states but have no effects of their own on the physical world, like the whistle of a steam engine.
The positions
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.
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.
Conceivable but impossible
Zombies may be conceivable, but they are not possible. Consciousness is physical, though we cannot see why from the armchair.
Arguments and objections
Zombies are possible, so physicalism is false
- 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.
Zombies are inconceivable
- 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.
Conceivable but impossible
- 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.
Who argued what
- Zombies are possible, so physicalism is false David Chalmers, Robert Kirk (early)
- Zombies are inconceivable Daniel Dennett, Robert Kirk (later)
- Conceivable but impossible Brian Loar, David Papineau, Ned Block
Where you stand
Could a perfect physical copy of you have no inner experience?
In surveys
Choose one to see how people answer.
Variations
The zombie's report
Your zombie twin writes a book arguing that consciousness is a hard problem and that zombies are conceivable. Since it is physically identical to you, it writes exactly the same words for exactly the same physical reasons. If your consciousness plays no role in producing your words, can your words be about your consciousness? This is the 'paradox of phenomenal judgment'.
Partial zombies
Could there be a being like you except that it feels no pain, while its other experiences are intact? Or one whose experience fades gradually as its neurons are replaced? These variations test whether consciousness comes in degrees or switches on all at once.
Go deeper
Epiphenomenalism looms
If a zombie twin does everything you do without consciousness, then your consciousness seems to do no work in producing your behaviour. This leads toward epiphenomenalism, the view that experience is caused by brain processes but causes nothing in turn. Many philosophers find this unacceptable, since it seems to mean that your pain is not why you say 'ouch'. Chalmers takes the problem seriously and explores ways of avoiding it.
Related ideas
Further reading and sources
- EncyclopediaStanford Encyclopedia of Philosophy: Zombies
- WikipediaPhilosophical zombie
- SurveyPhilPapers Survey, 2020 · question: Zombies; about 1,785 professional philosophers; accept or lean toward
- BookThe Conscious Mind, David Chalmers
- BookZombies and Consciousness, Robert Kirk
Open questions
- How do you know the people around you are not zombies?
- If your consciousness did nothing, would you ever be able to tell?
- Is imagining something good evidence that it could exist?