[h0l0cube]

P-zombies, conceptually, actually have no ghost in the machine, but are indistinguishable from sentient beings. Sentience and free will are two different things.

> they may have measurable effects in our physical reality

If there’s something external that interfaces with the physical universe, such an externality could be observed. It’s strange that we haven’t found such a force. But if it were to exist, in some parallel universe, that external force would have its own mechanics and its own chain of causality – its own physics so to speak. Dualism doesn’t get you to free will, it just means there’s physics we can’t observe. (Or perhaps there’s some superset universe that interfaces with that universe, and then it’s still determinism or stochastic processes all the way down.)