Imagine a being physically identical to you, with no inner experience at all

Philosopher David Chalmers asks us to imagine a 'zombie' that is a perfect physical duplicate of a conscious person, same brain, same reactions, but with nobody home inside, no experience at all. If such a being is even conceivable without contradiction, Chalmers argues, consciousness can't be fully explained by physical structure alone, since the zombie has every physical fact and still lacks it. The thought experiment remains a central challenge in the philosophy of mind.

— David Chalmers, The Conscious Mind: In Search of a Fundamental Theory — Oxford University Press, 1996
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