I think GP is referring to the idea that there is no yet identified physical mechanism that identifies the arising of consciousness in terms of properties of matter or energy, to which (if I understand GP correctly) physics restricts itself to. Leibniz put the objection to the mechanical materialist conception of consciousness/perception in 1714:
>One is obliged to admit that perception and what depends upon it is inexplicable on mechanical principles, that is, by figures and motions. In imagining that there is a machine whose construction would enable it to think, to sense, and to have perception, one could conceive it enlarged while retaining the same proportions, so that one could enter into it, just like into a windmill. Supposing this, one should, when visiting within it, find only parts pushing one another, and never anything by which to explain a perception. Thus it is in the simple substance, and not in the composite or in the machine, that one must look for perception.
> there is no yet identified physical mechanism that identifies the arising of consciousness in terms of properties of matter or energy
As far as I know, there's no proper definition of consciousness, and any time we have narrowed what consciousness may be (over the past few centuries) we have redefined consciousness so that it remains indefinable.
It seems strange to me to divide the universe into "meat inside bags of skin" and "things outside bags of skin" and presume one side of that split somehow possesses unique properties not subject to physical laws of matter and energy.
Physicalism and materialism aren't remotely equivalent. I see people making this mistake too often.
The dominant theory of consciousness in physics, neuroscience, neuro-physics (no surprise) and philosophy today is that conscious experience is the real intrinsic perspective of matter.
As such consciousness and all its contents are necessarily subjective, qualitative, and not reducible to purely quantitative physicalism.
Materialism then accounts for both consciousness and meaning (as measure of the significance of experiences relative to other experiences) in a way which physicalism cannot.
>One is obliged to admit that perception and what depends upon it is inexplicable on mechanical principles, that is, by figures and motions. In imagining that there is a machine whose construction would enable it to think, to sense, and to have perception, one could conceive it enlarged while retaining the same proportions, so that one could enter into it, just like into a windmill. Supposing this, one should, when visiting within it, find only parts pushing one another, and never anything by which to explain a perception. Thus it is in the simple substance, and not in the composite or in the machine, that one must look for perception.