Thursday, October 14, 2021

Disembodied existence and physicalism

Consider the following standard Cartesian argument:

  1. I can imagine myself existing without a body.

  2. So, probably, I can exist without a body.

  3. If I can exist without a body, I am not physical.

  4. So, I am not physical.

It is my impression that the bulk of physicalist concern about this argument focuses on the inference from (1) to (2). But it seems to me that it would be much more reasonable for the physicalist to agree to (2) but deny (3). After all, our best physicalist theory of the person is functionalism combined with a psychological account of personal identity. But on that theory, for me to exist without a body all that’s needed is for my memories to be transfered into a spiritual computational system which is functionally equivalent to my current neural computational system, and that seems quite plausibly possible.

The physicalist need not claim that I am essentially physical, only that I am in fact physical, i.e., that in the actual world, the realizer of my functioning is physical.


IanS said...

Wouldn’t physicalists by definition reject the possibility of anything spiritual, including a ‘spiritual computation system’?

An analogy: The abstract rules of (range limited, precision limited) arithmetic are implemented in actual physical calculators. But physicalists would surely reject the possibility of a ‘spiritual calculator’.

Alexander R Pruss said...

Physicalists would reject the actuality of anything spiritual, but I don't see why they should reject the possibility of spiritual things.

One popular story about the physical is that it is what exists in spacetime. But it seems easy to imagine Turing-complete computational mechanisms that do not exist in spacetime, and it would seem to be a heavy burden for a physicalist to bear to have to hold that such beings are impossible.

swaggerswaggmann said...

"But it seems easy to imagine Turing-complete computational mechanisms that do not exist in spacetime"

IanS said...


Fair point. Physicalists need not deny that non-physical things could exist, or even that they do exist. What they must deny is that non-physical things could have any causal influence on physical things.

So physicalists need not automatically deny that non-physical beings could non-physically observe me and set up a simulation of me on their non-physical computation devices.

But would such a simulated me be me? Of course, he would sim-answer to sim-IanS if sim-asked, and he would feel, in his simulated way, just as IanS-ish as I do. But would that be enough to make him me? The beings running the simulation would be able to see that we were at least numerically different. I guess I’m doubting the approach to personal identity suggested in the post. Maybe a bit of externalism is required.

Alexander R Pruss said...


On standard takes on functionalism plus the psychological theory of identity, if the nonphysical beings made a simulation of you, and simultaneously destroyed you, the simulation would be you, as it would have your memories and there would be no fission.

If they didn't destroy you, we would have a case of fission. The most common thing to say on psychological theories of identity seems to be that in cases of fission, the original person perishes and two new persons come into existence. (That said, it does seem absurd to me to think that you could kill someone simply by reading their data and putting it in a simulation.)