[Some] versions of identity panpsychism are holistic in that they invoke fundamental physical entities that are not atomic or localized. One such view combines identity panpsychism with the monistic view that the universe itself is the most fundamental physical entity. The result is identity cosmopsychism, on which the whole universe is conscious and on which we are identical to it. (Some idealist views in both Eastern and Western traditions appear to say something like this.) Obvious worries for this view are that it seems to entail that there is only one conscious subject, and that each of us is identical to each other and has the same experiences. There is also a structural mismatch worry: it is hard to see how the universe’s experiences (especially given a Russellian view on which these correspond to the universe’s physical properties) should have anything like the localized idiosyncratic structure of my experiences. Perhaps there are sophisticated versions of this view on which a single universal consciousness is differentiated into multiple strands of midlevel macroconsciousness, where much of the universal consciousness is somehow hidden from each of us. Still, this seems to move us away from identity cosmopsychism toward an autonomous cosmopsychist view in which each of us is a distinct constituent of a universal consciousness. As before, the resulting decomposition problem seems just as hard as the combination problem.
Perhaps the most important version of identity panpsychism is quantum holism. This view starts from the insight that on the most common understandings of quantum mechanics, the fundamental entities need not be localized entities such as particles. Multiple particles can get entangled with each other, and when this happens it is the whole entangled system that is treated as fundamental and that has fundamental quantum-mechanical properties (such as wave functions) ascribed to it. A panpsychist might speculate that such an entangled system, perhaps at the level of the brain or one of its subsystems, has microphenomenal properties. On the quantum holism version of identity panpsychism, macrosubjects such as ourselves are identical to these fundamental holistic entities, and our macrophenomenal properties are identical to its microphenomenal properties.
This view has more attractions than the earlier views, but there are also worries. Some worries are empirical: it does not seem that there is the sort of stable brain-level entanglement that would be needed for this view to work. Some related worries are theoretical: on some interpretations of quantum mechanics the locus of entanglement is the whole universe (leading us back to cosmopsychism), on others there is no entanglement at all, and on still others there are regular collapses that tend to destroy this sort of entanglement. But perhaps the biggest worry is once again a structural mismatch worry. The structure of the quantum state of brain-level systems is quite different from the structure of our experience. Given a Russellian view on which microphenomenal properties correspond directly to the fundamental microphysical properties of these entangled systems, it is hard to see how they could have the familiar structure of our macroexperience.
The identity panpsychist (of all three sorts) might try to remove some of these worries by rejecting Russellian panpsychism, so that microphenomenal properties are less closely tied to microphysical structure. The cost of this move is that it becomes much less clear how these phenomenal properties can play a causal role. On the face of it they will be either epiphenomenal, or they will make a difference to physics. The latter view will in effect require a radically revised physics with something akin to our macrophenomenal structure present at the basic level. Then phenomenal properties will in effect be playing the role of quiddities within this revised physics, and the resulting view will be a sort of revisionary Russellian identity panpsychism.