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 not valid as a deductive argument, but it is Bayesian evidence in favour of naturalism. Also, the details of the observed effects of brain damage provide even more for naturalism rather than nonnaturalism.

It's not valid as a deductive argument, but it is Bayesian evidence

The "not a logical disproof" defense can be used against more or less all arguments drawing on empirical science. It would be more charitable to assume Richard means something like "the probability of brain damage by region delicately affecting particular parts of information processing is reasonably high given belief in souls." Although that still looks quite wrong. The "radio" analogy would not predict a speech center, or other patterns of brain damage and impairment that look like interfering with computation, not transmission.

22SilasBarta14y

You can say that about pretty much anything labeled a "fallacy". For example, the "appeal to authority fallacy" --> yes, an authority on the matter is not guaranteed to be right, but their opinion is Bayesian evidence in favor of such beliefs. Fortunately, a poster already wrote an article with that thesis.

4RichardChappell14y

That's surely going to depend on the details of the non-naturalist view. Epiphenomenalism, for example, makes all the same empirical predictions as physicalism. (Though it might be harder to combine with a "soul" view -- it goes more naturally with property dualism than substance dualism.) But even Cartesian Interactionists, who see the brain as an "intermediary" between soul and body, should presumably expect brain damage to cause the body to be less responsive to the soul (just as in the radio analogy). Or are you thinking of "non-naturalism" more broadly yet, to include views on which the brain has nothing whatsoever to do with the mind or its physical expression? I guess if one had not yet observed the world at all, this evidence would slightly lower one's credence in non-naturalism by ruling out this most extreme hypothesis. But I take it that the more interesting question is whether this is any kind of evidence against particular non-naturalist views that people actually hold, like Cartesian Interactionism or Epiphenomenalism. (And if you think it is, I hope you'll say a bit more to me to explain why...)

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