RE: "But I can give you one important example of what a zombie would be, if there could be zombies: A robot that can pass the Turing Test: act and talk in the world, indistinguishably (in what it does) from any of us, for a lifetime -- but without feeling anything at all whilst doing it all (just like a stone)."

But this seems self-contradictory.  How could a being (assuming it is one) be "indistinguishable" from any of us yet not feel - if what we do includes feeling?  'Well' one might answer, 'we can't see "inside" it, so it might be doing all these "human" things (!) but not feeling.'  But that only begs the question of if/how we see 'Inside' anyone. (The word 'indistinguishable' is a trap here, I think. In effect we are assuming what has to be proved - that something can be  'indistinguishable'  from a human yet not be one. But how do we make sense of that idea?)

RE: 'Probably yes, a worm can feel (no scare-quotes needed), which means exactly the same thing as that the worm is conscious.'

Well, if this is the definition of consciousness, do we humans 'feel' in the same way?  If so, is human consciousness the same as worm consciousness (or, say, amoeba consciousness)? If not, there must be two (or more) forms of consciousness. How do they differ? And are we really entitled to call them all by the same name (ie consciousness)? Surely, only if we knew that all creatures great and small 'feel' the same way we 'feel' - which of course we can never know. 

RE: 'Consciousness does not need to be "defined": it just needs to be pointed to.'

But how does one point to something if one doesn't know what it is?  Could I point to a bird if I didn't know what a bird was?  I might in fact be pointing to the squirrel on the branch beside it. And replying, 'Well, we "just know" what consciousness is' is to my mind another trap. We tend to think we "just know", but when we try to state what we "just know" there is endless debate and confusion. For the very good reason that the idea is in fact not easily knowable at all but extremely elusive. 

DA