Robert Kane famously physicalistically grounds free will in quantum events in the brain. Free choice, on Kane’s view, is constituted by rational deliberation involving conflicting motivational structures with a resolution by an indeterministic causal process—a causal process that Kane thinks is in fact physical.
Here is a problem. Suppose Kane’s view is true. But now imagine a possible world with a physics that is like our quantum physics, but where panpsychism is true. The particles are conscious, and some of them engage in libertarian free choices, with chances of choices exactly matching up with what quantum mechanics predicts. The world still has people with brains, in addition to particle-sized people. The people with brains have particles that are persons in their brains. Moreover, it turns out that those indeterministic causal processes in the brains that constitute free choice are in fact the free actions of the particle-sized people in the breains.
All of Kane’s conditions for freedom will be satisfied by the people with brains. For the only relevant difference is that the quantum-style causal processes are choice processes (of the particle people). But these processes are just as indeterministic as in our world, and it’s the indeterminism that matters.
But the actions of the brain possessors in that world wouldn’t be free, because they would be under the control of the particle people in the brains. We could even suppose, if we like, that the particle people know about brains and want to direct the big people in some particular direction.
One could add to Kane’s account the further condition that the indeterministic causal processes in the brain are not constituted by the free choices of another person. But this seems ad hoc, and it is not clear why this one particular way for the indeterministic causal processes to be constituted is forbidden while any other way for them to be constituted is acceptable. The details of how quantum indeterministic processes work, as long as they are truly indeterministic and follow the quantum statistics, should not matter for free will.
This problem applies to any physicalist account on which free choices are grounded in quantum processes.
There is a way out of the problem. One could accept a pair of Aristotelian dicta:
All persons are substances.
No substance is a part of another substance.
But it is not clear whether the acceptance of these dicta is plausible apart from the fuller Aristotelian metaphysics which holds that all substances are partially made of non-physical forms. In other words, it is not clear that acceptance of (1) and (2) can be well motivated within a physicalist metaphysics.
