WIRED: Getting back to the theory, is your version of panpsychism truly scientific rather than metaphysical? How can it be tested?

Koch: In principle, in all sorts of ways. One implication is that you can build two systems, each with the same input and output — but one, because of its internal structure, has integrated information. One system would be conscious, and the other not. It’s not the input-output behavior that makes a system conscious, but rather the internal wiring.

The theory also says you can have simple systems that are conscious, and complex systems that are not. The cerebellum should not give rise to consciousness because of the simplicity of its connections. Theoretically you could compute that, and see if that’s the case, though we can’t do that right now. There are millions of details we still don’t know. Human brain imaging is too crude. It doesn’t get you to the cellular level.

The more relevant question, to me as a scientist, is how can I disprove the theory today. That’s more difficult. Tononi’s group has built a device to perturb the brain and assess the extent to which severely brain-injured patients — think of Terri Schiavo — are truly unconscious, or whether they do feel pain and distress but are unable to communicate to their loved ones. And it may be possible that some other theories of consciousness would fit these facts.

WIRED: I still can’t shake the feeling that consciousness arising through integrated information is — arbitrary, somehow. Like an assertion of faith.

Koch: If you think about any explanation of anything, how far back does it go? We’re confronted with this in physics. Take quantum mechanics, which is the theory that provides the best description we have of the universe at microscopic scales. Quantum mechanics allows us to design MRI and other useful machines and instruments. But why should quantum mechanics hold in our universe? It seems arbitrary! Can we imagine a universe without it, a universe where Planck’s constant has a different value? Ultimately, there’s a point beyond which there’s no further regress. We live in a universe where, for reasons we don’t understand, quantum physics simply is the reigning explanation.

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