Robert Kirk (in the Stanford Encyclopedia of Philosophy) explains that: "Zombies are exactly like us in all physical respects but have no conscious experiences: by definition there is ‘nothing it is like’ to be a zombie." Do I have conscious experiences? (And have I asked enough rhetorical questions yet?) Like Hume, I have a hard time catching myself when I try to focus on my mental life. It's as if there is an 'I' there, but one that always gets away when I turn my attention in what seems to be the right direction. Mostly I'm conscious of the things around me: books, papers, pictures, a computer, and so on. I'm not conscious of having experiences of these things, just conscious of the things themselves. To have a conscious experience I seem to have to press my thumb into the palm of my hand or pinch myself. (That is, simply seeing what's around me doesn't really feel like what is normally called having an experience.) But then I still feel the thing itself (my thumb pressing, my fingers pinching), not 'a pressing sensation' or anything like that. (Well, maybe it's like that, but that seems like a very unnatural way to describe what I actually experience.) Distant hazy clouds of warmth and mild discomfort float around the edges of my body, but they barely seem to exist until I turn my attention on them, so that doing so seems to distort the evidence. Even my own thoughts are like this. I think (it seems to me, phenomenologically, not philosophically) in propositions, not sentences. They aren't in color or any particular font or accent. I suppose I think in a man's voice, but how could it be either male or female when I don't usually hear it at all. Thinking is more like reading your own mind than hearing yourself talk. (Although it's more like hearing than reading, at least for me.) It's an invisible, insensible process.
Is there something it is like to be me? Being me, it seems to me, is doing the things I do. So no one else can actually be me because only one person can sit where I am sitting, look like this, be this tall, weigh this much, think these thoughts, feel these emotions and sensations, etc., all at the same time. But you would know exactly what it is like to be me if you lived an exactly similar life, doing exactly the same things (including reacting to things in the same way, taking offense at the same things, being amused by the same things, and so on).
Is there then something that it is like to be a statue or a mountain? They do things: exist, crumble a bit from time to time, cast shadows, etc. Could I say that being a hill is like being a mountain, and being a mannequin is like being a statue? It doesn't feel the same, because not feeling at all is part of what it is to be a mountain or a statue. I think it doesn't really make sense to talk about what it's like to be a mountain because doing so implies that mountains experience things, are sentient. But this suggests to me that it is no help at all to explain sentience in terms of there being something that it is like to be the sentient thing. It's like defining death in terms of loss of life. What is conscious or sentient is, odd (or tiresomely Wittgensteinian) as it might sound, determined or dictated by grammar. Grammar (patterns of sense, or just language) tells us what is conscious and what is not. At least grammar marks out a kind of space within which it makes sense to call things conscious, and makes some tests of consciousness more plausible, more reasonable, than others. To ask of something that passes these tests, as I do, whether it is really conscious is then either to ask for a stricter test or to make a mistake.
(If this seems like a terrible argument, I apologize. It's not really intended as an argument at all. It's a record of my own train of thought, and where it goes quickly is not where I want to gloss over difficulties but where I raced to the end because the way seemed so clear to me. I make no claim that it is clear in any other sense.)