Software developer, Chartered Accountant, philosophy graduate and (occasionally) rationalist. Good Grief, Linus is to reclaim the Peanuts character Linus Van Pelt for reason. He is the brightest child in the comic strip but also strangely spiritual, bible quoting and pumpkin worshiping. Note that he is often seen with a security blanket.
Continuing to summarise responses in Susan Blackmore's excellent Conversations on Consciousness, I now come to the problem of the philosopher's zombie - a being indistinguishable from any other human being but which lacks any mental content, such as feelings, thoughts and, in fact, consciousness: do you believe in the possibility of the philosopher's zombie?
As before I will only offer outlines of and quotes from their answers; buy the book for the Full Monty. Be aware that quote context is important, and I'm focussing on those comments that seem particularly relevant to me.
Ned Block: Block distinguishes between beings that are functionally equivalent to us, like his famous China Brain thought experiment, which he supposes functionalists would think had a phenomenology, but he doesn't know (he thinks possibly not), and beings that are physically just like us, which I think was Chalmers original idea. "My view is that no-one who takes the biological basis of consciousness seriously should really believe in that kind of zombie." So, no to the second type.
David Chalmers: "I think they're probably not possible in the sense that no such thing could ever exist in this world." He doesn't think it's contradictory ("at least in the imagination") that a p-zombie could exist, however, so he denies they're logically impossible. I'm not sure that conceivability quite helps here, though.
Patricia & Paul Churchland Pat - "Of course it's logically possible, but that's not interesting...we're interested in knowing whether or not it's empirically possible. And it does not seem to be, so far as we know." Paul says you can imagine a universe in which electromagnetic waves are bouncing around but it's still pitch black, but this doesn't get away from what light is as a matter of fact.
Daniel Dennett: "...we get a bifurcation of theorists into those who take the zombie hunch seriously, and those who, like myself, have sort of overcome it. I can feel it, but I just don't have it any more."
Susan Greenfield: "No, I think that consciousness is part of feeling, part of seeing; so I don't think you can separate out vision and emotion from consciousness, no."
Stuart Hameroff: A certain amount of talking around the problem, but basically, yes, because he thinks there is something specific that 'adds' consciousness - "...consciousness, or perhaps something proto-conscious, is fundamental to the universe..." Hameroff has some idea about microtubules generating consciousness, so anything that functioned the same as humans, but without these, wouldn't be conscious. The difficulty is to know what these add, of course. I think he would say that anything physically identical could not be a p-zombie.
Christof Koch: "No...But there's going to be something specific about the neurons that give rise to consciousness..."
Thomas Metzinger: "I am not a possible world surfer. As long as 'consciousness' is such an ill-defined term, many things remain conceivable."
Kevin O'Regan: "...I knew I was a robot...", which I think means, no, there is no difference between us and p-zombies.
Roger Penrose: "A philosopher's zombie is something which I would say couldn't exist." Possibly some confusion surrounding the distinction that Ned Block draws.
Vilayanur Ramachandram: "No, they're not possible. I think if you create a creature which is identical to us - it doesn't matter how you create the zombie - it'll be fully conscious in the human sense."
John Searle: He is asked if the p-zombie could in principle exist and he answers, "In principle, sure." He thinks there is something extra that adds the consciousness, but it's not clear to me if 'in principle' means logically or empirically. Again, because of his anti-functionalist stance, I think he's talking about the possible existence of a functional zombie.
Petra Stoerig: "I think they are logically possible...as a biologist I think it's a waste of all the trees that go into this paper, because it's not biologically possible."
Francisco Varela: "I just don't grock it...I say it's just a problem that you create by inventing problematic situations. So what?"
Max Velmans: "...I think I would personally rule out the possibility that it didn't experience as we do."
Daniel Wegner: Not really asked, but seems to be an advocate of humans as robots, so probably no.
I think I was quite surprised that they all thought that physically identical beings could not be internally empty, but I suppose this just shows that they are all physicalists, so any other conclusion would be incoherent. There were one or two demurrals on the idea of a functionalist zombie (functionalism, very basically, is the theory of mind that posits that a mind is determined by what it does, rather than what it is made of). I think Ned Block, Hameroff and Penrose thought that this could exist. I'm pretty certain about the first type and less sure about the second, simply because I'm less sure about functionalism than I am about physicalism. In fact, I could imagine that there is something special about the particular combination of material and function that gives rise to consciousness, although I'm baffled what microtubules might add. I think I'm still much more inclined to believe that complexity in function will deliver consciousness than some ineffable I-don't-know-what in the biological make-up, because whatever biological detail is added, it still doesn't seem to solve the problem we're being asked to solve - intentionality, qualia and so on.