I don’t get (any of) the arguments against mind-brain identity theories.

It’s usually argued that multiple realisability kills MBIT (see also this post). In a talk I attended it was stated as follows:

If pain = C-fiber activation, and extraterrestrials don’t have C-fibers, does it mean they can’t have pain?

Well, no. There seems to be another, less drastic way out. Is there any reason to assume that all pains are the same? Is there any reason why any pain is ever the same?

Pain is a category; just like every snowflake is unique, every pain could be unique, and uniquely and exactly corresponding to a certain physical (brain) state.

Am I missing the crux of the argument?

  • Yes, you are missing it. The argument is against type identity, not token identity. If pain is a category (type), and has a physical correlate as such (type identity) the differences in different pains are irrelevant. If each pain has its own physical correlate, we have, at best token identities, and mental category pain has no physical correlate.
    – Conifold
    Jun 1, 2019 at 17:49
  • @Conifold Good. Though this interpretation makes type physicalism sound absurd. They cannot possibly hold that there is only one instance of pain? I think token physicalism refers to “c-fibers and pain” are instances of the same category but not the same, not to the phenomenal quality “pain” itself. Jun 1, 2019 at 18:06
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    Type identity theory holds that there is some common core to all pains, which is constitutive of something being a pain, rather than, say, surprise or pleasure, and this common core has a physical correlate, some pattern of neuronal activity, perhaps. Without that we must either hold that mentalistic predicates are ontologically superficial, like fruits and vegetables (token physicalism), or that there exist mental properties irreducible to physical ones (property dualism). See IEP Type vs. Token Identity.
    – Conifold
    Jun 1, 2019 at 18:18
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    @Conifold I see. If you put it like that, the significance of the entire mind-body problem seems to be reduced to appropriately defining categories. I mean, saying “if an ET does not have C-fibers, does it mean it cannot have pain?” seems no more deep than asking “if ever we find a planet that harbours living organisms that look and function like trees but not carbon-based are they to be called trees?” Jun 1, 2019 at 18:24
  • We are not free at defining categories if we want them to reflect what is out there. The question about the proper vocabulary for a good theory of mind is highly non-trivial and substantive. It took us a long time to figure out that what is constitutive of all waters is their chemical composition, H20. Figuring out something like that for the pain, or discovering that physical/chemical vocabulary is insufficient for the task of building a theory of mind, would be a major advance.
    – Conifold
    Jun 1, 2019 at 18:30


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