HP:MOR and the Radio Fallacy

RichardChappell

No plot spoilers here, just wanted to flag a bit of poor reasoning that shows up in Chapter 39:

I shouldn't have believed it even for all of thirty seconds! Because if people had souls there wouldn't be any such thing as brain damage, if your soul could go on speaking after your whole brain was gone, how could damage to the left cerebral hemisphere take away your ability to talk?

This is a surprisingly common fallacy. Just because X depends on Y, it doesn't follow that X depends on nothing but Y. A phenomenon may involve more than just its most obvious failure point.

To illustrate: Suppose I'm trapped in a box, and my only way to communicate with the outside world is via radio communication. Someone on the other end argues that I don't really exist -- "There's no person beyond the radio receiver, for if there was then there wouldn't be any such thing as damaged radios!" Pretty silly, huh? But people say this kind of thing in defense of physicalism all the time.

(N.B. This is not to defend the existence of souls. It's just to point out that this particular argument against them is invalid.)

No plot spoilers here, just wanted to flag a bit of poor reasoning that shows up in Chapter 39:

I shouldn't have believed it even for all of thirty seconds! Because if people had souls there wouldn't be any such thing as brain damage, if your soul could go on speaking after your whole brain was gone, how could damage to the left cerebral hemisphere take away your ability to talk?

This is a surprisingly common fallacy. Just because X depends on Y, it doesn't follow that X depends on nothing but Y. A phenomenon may involve more than just its most obvious failure point.

(N.B. This is not to defend the existence of souls. It's just to point out that this particular argument against them is invalid.)

It's that particular kinds of brain damage can take away particular mental abilities, and there's a consistent correlation between the damage to the brain and the damage to the mind.

And particular damage to a radio receiver distorts the received signal in particular ways. So that argument isn't much help.

Well, the question is, do the specific effects of damage look more like the effects that the "radio receiver" hypothesis would predict, or the ones that the "electronic brain" hypothesis would predict?

There is a big difference between an audio distortion and a semantic distortion. The radio-receiver hypothesis predicts that we can introduce audio distortion, but not that we can make the voice stop talking about vegetables. If we can only get the former sort of effect, then we are messing with a device that didn't understand vegetables i... (read more)

27gjm14y

I don't understand. Did you read the rest of what I wrote, where I gave some specific examples of the kind of damage we're talking about? (Note: they weren't intended to be neurologically perfectly accurate.) Do you not agree that if you had a device that produced such effects when damaged, it would be grossly unreasonable to think it was a radio rather than an AI? [EDITED to add: Of course I agree that there are situations, quite different from what we see in the real world, that could also -- just barely -- be described by saying "particular kinds of damage to the brain produce particular kinds of apparent damage to the mind", but where that would not be very strong evidence that the mind is implemented by the brain. For instance, you damage one bit of the brain and the person's voice goes squeaky; you damage another and all the consonants go away. What's different about the real world is that particular kinds of brain damage have particular semantic signatures; they are bound up with the content of what's being thought or said. It's still consistent with all this that the mind isn't implemented only by the brain. If every aspect of human thought required cooperation between the brain and the soul, you could still get the sort of thing we actually observe. But let's distinguish between "there are some theories of souls that are consistent, at least in principle, with these observations" and "these observations do not constitute a good reason not to believe in souls". The former is probably true, the latter not.]