The mere logical possibility of such a being creates a huge problem for physicalism. If a zombie is physically identical to a conscious person, then it means consciousness is an extra ingredient, not explained by the physical arrangement of matter. It would suggest that consciousness is 'epiphenomenal'—a useless byproduct of brain processes, like the heat from a computer, having no effect on the world. And that seems deeply counterintuitive. Why would evolution produce such a rich inner world if