I don't think your point 2 is directly analogous to his point 2.
Because a world where things do not fall down is not physically identical to a world in which they don't.
I think the point of arguing about p-zombies is this. Do you believe it's possible for a human being to exhibit all the external characteristics of consciousness without an internal conscious experience? And if you believe that's true, then you can posit a world which is physically indistinguishable from our world through any experiment in which consciousness simply does not exist, because, as far as I know, there is no test that can prove that an individual does have an internal consciousness, and isn't merely mimicking it. Most arguments that p-zombies don't exist sort of rely on the internal conscious experience of the person making it, which no one else has access to -- "I have an internal conscious experience of the world, other people are similar to me and so they must also have those experiences."
That is _not_ true about a world in which gravity does not exist for obvious reasons. That universe would be very different from ours and easily distinguishible through experiment.
I think his point does hinge on whether it's possible for p-zombies to exist, but it's not as silly as you all are making it out to be, and it is not begging the question.
I actually think his weakest point is part 3 and 4, because I think mostly the problem is that we don't really have good definitions of consciousness and related concepts let alone a complete physical explanation of their origins, and his whole argument hinges on the fact that we currently don't have a way to test for internal conscious experience, but I think that might not always be true.
Because a world where things do not fall down is not physically identical to a world in which they don't.
I think the point of arguing about p-zombies is this. Do you believe it's possible for a human being to exhibit all the external characteristics of consciousness without an internal conscious experience? And if you believe that's true, then you can posit a world which is physically indistinguishable from our world through any experiment in which consciousness simply does not exist, because, as far as I know, there is no test that can prove that an individual does have an internal consciousness, and isn't merely mimicking it. Most arguments that p-zombies don't exist sort of rely on the internal conscious experience of the person making it, which no one else has access to -- "I have an internal conscious experience of the world, other people are similar to me and so they must also have those experiences."
That is _not_ true about a world in which gravity does not exist for obvious reasons. That universe would be very different from ours and easily distinguishible through experiment.
I think his point does hinge on whether it's possible for p-zombies to exist, but it's not as silly as you all are making it out to be, and it is not begging the question.
I actually think his weakest point is part 3 and 4, because I think mostly the problem is that we don't really have good definitions of consciousness and related concepts let alone a complete physical explanation of their origins, and his whole argument hinges on the fact that we currently don't have a way to test for internal conscious experience, but I think that might not always be true.