Tuesday, October 30, 2018


Let me tell a story. Some neuroscientists detected a physically novel form of radiation, M-rays, that is emitted by brains of subjects who are thinking consciously. They discovered this much like X-rays were discovered, namely by finding something impinging on equipment in the lab in a way that could be explained by conventional physics. Further experiment showed that M-rays are not emitted by anything that clearly isn’t conscious. Moreover, the line between animals that emitted M-rays and animals that didn’t seemed to correspond to a noticeable difference in cognitive sophistication. Finally, in humans the M-rays turned out to be modulated in a way that has a natural one-to-one correspondence with the phenomenal states reported by the conscious subjects, so that the scientists eventually learned to discern from the M-rays what the subject’s conscious state is. (The CIA was very interested.)

In this case, it would be eminently reasonable for a physicalist to conclude that consciousness is the emission of M-rays.

This thought experiment shows that mysterians like Colin McGinn are mistaken in holding that no discovery we could make would solve the hard problem of consciousness.

But of course few physicalists actually expect to find a physically novel phenomenon in the brain.


Stephen Tweedale said...

Would M-rays really solve the hard problem? It seems the question "why are M-rays conscious?" remains. Chalmers makes this point in "Moving Forward on the Problem of Consciousness":

"The worry is as follows: for any given interactionist theory, it seems that we can remove the facts about experience, and still be left with a coherent causal story. Take Eccles' theory on which "psychons" in the mind affect physical processes in the brain. Here one can tell a perfectly coherent causal story about psychons and their effect on the brain without ever mentioning the fact that psychons are experiential. On this story, psychons will be viewed as causal entities analogous to electrons and protons in physical theories, affected by certain physical entities and affecting them in turn; and just as with protons and electrons, the fact that psychons have any experiential qualities will be quite inessential to the dynamic story. So one can still give a causal explanation of behavior that does not involve or imply experience. The same would go for a Cartesian theory involving ectoplasm, for Libet's proposal involving a "conscious mental field", and even for the theories that Stapp and Hodgson advocate."

Alexander R Pruss said...

But Chalmers goes on to give a solution, namely that the categorical basis of the causal powers could be innately experiential.

Stephen Tweedale said...

Yes, but the thing that solves the hard problem isn't discovery of the M-rays as such (or any other novel consciousness-related physics), it's imputing experience to the intrinsic nature of M-rays. Chalmers thinks that physics only describes the extrinsic character of its basic entities. If physics only describes M-rays extrinsically and M-rays only solve the hard problem if they are intrinsically experiential, then the discovery of M-rays wouldn't solve the hard problem.

Alexander R Pruss said...

Causal powers aren't extrinsic to the item that has them, on my view. I am not sure this affects Chalmers' point, though.