Consciousness poses the most baffling problems in the science of the mind. There is nothing that we know more intimately than conscious experience, but there is nothing that is harder to explain.

I think the existence of zombies would contradict certain laws of nature in our world. It seems to be a law of nature, in our world, that when you get a brain of a certain character you get consciousness going along with it.

Why should physical processing give rise to a rich inner life at all? It seems objectively unreasonable that it should, and yet it does.

How does the water of the brain turn into the wine of consciousness?

Studying consciousness tells us more about how the world is fundamentally strange. I think we have a few revolutions to go yet before we get to the bottom of it.

Sense data are much more controversial than qualia, because they are associated with a controversial theory of perception - that one perceives the world by perceiving one's sense-data, or something like that.

Because the idea of zombies seems to make sense, and seems to, in a certain sense, be possible, I think one can use that to argue against the thesis that everything is purely physical. Now many people, I think, agree that the idea of zombies are conceivable, including people who want to be physicalists.