This is the exact point where I always get off the hard problem p-zombie train:
> It is possible at least in principle, he says, for there to be a world physically identical to our own down to the last particle, but where there are none of the qualia of conscious experience.
No. I don't consider this possible even in principle. Imaginable, yes, possible? No.
One example is enough to dispose of any contradiction, so here's one: in this contrafactual world, a person says "I feel the sun warming my skin". Since qualia do not exist in the contrafactual, in that world, the person is a liar. In this world, he is not. That is a difference: QED.
Ah, but you may say: this is not a physical difference. No, perhaps not. But it most rapidly results in one. Liars and honest men are not the same. Especially when they lie about having any and every experience of existence. This is a difference which must perforce produce change: it beggars the imagination to picture such a world careening forwards identical to our own.
> It is possible at least in principle, he says, for there to be a world physically identical to our own down to the last particle, but where there are none of the qualia of conscious experience.
No. I don't consider this possible even in principle. Imaginable, yes, possible? No.
One example is enough to dispose of any contradiction, so here's one: in this contrafactual world, a person says "I feel the sun warming my skin". Since qualia do not exist in the contrafactual, in that world, the person is a liar. In this world, he is not. That is a difference: QED.
Ah, but you may say: this is not a physical difference. No, perhaps not. But it most rapidly results in one. Liars and honest men are not the same. Especially when they lie about having any and every experience of existence. This is a difference which must perforce produce change: it beggars the imagination to picture such a world careening forwards identical to our own.
This is not physics. It is fantasy.