Anon: “Godfrey-Smith worries about the feeling of having separate streams of mind, due to trying to imagine what being an octopus is like.”
“Have” is a weasel-word. The only “haver” is the feeler — unless there are multiple co-habiting feelers, in which case the “haver” is the (shared) body, and that geographic “having” is not a mental state, (i.e., not a felt state) but just a geographically proximal (potentially even simultaneous) pair of distinct states, co-colonizing the same somatic substrate.
I think the crucial intuition is that a feeler cannot feel another feeler’s feeling. It can have a similar feeling, in response to the same external input; it can have it simultaneously (or successively); the feeling can feel as if it were another feeler’s feeling. But it is not, and cannot be another”s feeling.
And that is part of the nature of feeling (hence of having a mind): Feeling is a state (generated by a neural substrate). A state that it feels like something to be in. A felt state is always “dual” in that there is the feeler and the feeling. (This is vaguely and insufficiently analogous to moving: there is the thing that is moving, and there is the moving itself.) There cannot (pace Freud) be an “unfelt feeling” any more than there can be an “unmoved moving.”
But feeling is not contemplation by a Cartesian ego. That’s a cognitive capacity that some feelers (e.g., humans, verbally, and probably many other vertebrates and perhaps some invertebrates, nonverbally) have; and other feelers (e.g. amphyoxus, or annelids) don’t. But the duality (some prefer to call it, unhelpfully, “relationality”) is inherent in the nature of feeling itself.
“Co-habitation” and geographic overlap are certainly possible, but that has to do with the causal substrate of the feeling(s): the causal mechanism that is generating the feeling(s). If ever there was a category error, it’s that of conflating (1) the neural substrate that is generating the feeling with (2) the feeler of the feeling. The feeler is a part of the feeling generated. And, absent “telepathy,” a feeler cannot literally feel a feeling that is generated by another neural substrate — whether a nearby or even a partly overlapping one: Siamese twins who share part of their brain so that they both feel it when their conjoined arm is touched are not feeling the same feeling, just an otherwise almost identical one — only almost, because the twins are not spatially identical, otherwise we would be deeply into the metaphysics of indiscernibles!
Anon: “He uses trying to imagine split brain people but –for him and for me — that is not entirely satisfactory… he has driven his car safely over a familiar route and really can’t recall any memory of having done so: i mean he knows he did; its not a surprise, but really it was absent his conscious attention.”
We can do things without feeling we are doing it, or without remembering that we felt we were doing it, or even without remembering or otherwise knowing we did it. And I suspect that that can be true of us simultaneously (especially for our vegetative functions, like breathing, which we can do both deliberately and feelingly, and automatically without feeling it). In that sense, we are all octopus-like time-sharing multi-processors, simultaneous and successive (like the split-brain).