> "What in the devil's abstraction is this? Souls? Really?"
> Friend posts meme about forum post: "On building Omelas for shrimp; the implications of diversity-oriented theories of moral value on factory farming"
> Read's linked intro to Theory of Mind in the post
> Remembers arguments in this article
> Immediately convinced that soul theory is likely the best explanation of personal identity
I guess it just seems to me that the sorts of intuitions you're relying on here are the exact sort of intuitions we ought to doubt if naturalism is true - I see no particular reason why evolution would lead us to be able to have any sort of direct, unimpeachable insight into our own mental reality, and many reasons why such insight would even be negatively advantageous. Abandoning physicalism, which has been overwhelmingly successful in surviving many similarly structured challenges, and embracing an entirely new framework (one which seems unable, even in principle, to yield the sort of concrete empirical understanding physicalism at least anticipates) in response to these concerns seems obviously unwarranted to me. Why not just accept the idea that you might be wrong about whether two minds could exist alongside each other, or whether there is some further fact re: the experiencer? Especially since we know for a fact that human beings are capable of shedding such a sense in certain conditions?
To add to these great points: whatever intensity of intuition I've ever had supporting dualism was far weaker than many other intuitions I've rejected because of incompatibility with scientific findings and/or philosophical arguments. e.g. "The Earth is stationary and the sun moves across the top of it", "Different species are intrinsically distinct and unrelated to one another", "There could not be more permutations of a standard deck of cards than grains of sand in the Sahara". I'm not even convinced that I would have had an intuition that I was a separate substance ("soul") if I hadn't been taught it by a religious / Christian-influenced secular culture.
Very interesting. I share your intuition about the necessity of an experiencer, but I tend to be skeptical of those feelings. For your second argument: 1) I feel that the use of 'who' in point 3 assumes the conclusion; 2) if we run this argument about two identical red shirts, need we posit an essence of shirt that enables the shirts to differ?; relatedly 3) if you did in fact have two minds, there would necessarily be a physical difference for them both to be instantiated--otherwise point 1 is also assuming the conclusion.
1) well, they have to differ in some way. What way could they differ in regards to if they have the same experiences and are physically the same.
2) there couldn't be two different identical red shirts. What would that even mean? They couldn't be in the same location and physically identical or they'd be impossible to distinguish.
3) But it seems conceivable that I'd have two minds that are instantiated on the same physical substance.
1) This is right to my point. Could you run two identical software programs on the same hardware, using the very same bits? Can a hand perform two identical tasks at the same time, using the same materials? I don't know what motivates the notion that you could have two identical minds running on the same brain, being physically identical in every way but differing in who is doing the experiencing, unless you are already assuming some metaphysical weirdness, in which case the weirdness you're assuming is what informs the conclusion that two minds can share the same physical hardware.
2) I was talking about qualitative, not numerical identity.
3) That does not seem conceivable to me. I agree with Vikram, from whom I just learned the phrase ipse dixit (which has that lovely property of sounding like what it means).
I'm curious to probe your intuition here. Is there a limit to how many minds you think can be numerically identical save for the soul component? A thousand? An infinite number?
2) For two things to be numerically distinct they must differ in respect to some quality, if we accept the indiscernability of indenticals.
3) It seems conceivable to me. We know your brain already generates one mind. If you discovered that it generates another one, does that really seem like a square circle. I think it could be an infinite number, and I find that intuitively obvious.
Surely there are some constraints to your version dualism? It can't be that souls can be imputed wherever one likes. I give non-physicalism plenty of credence--I am usually a monist but not a physicalist--but if you want me to share in your intuition you should pump it a bit, maybe give some examples of other instances in which "two, or in fact any number, of identical things can share all physical properties, except an imperceptible essence." If there are none in your accounting, then more needs to be said about why. Actually, I could agree that we have souls on the basis of my own intuition that I have an inner experiencer of things, but disagree that I could have two identical ones. Could I not simply say that if they are identical in every way, they are the same mind? If you say 'no, there's a different who in mind #2' then we're back to the fact that you're assuming the who-ness. It also seems perfectly coherent to me that I could have a mind which is not physical, but which nonetheless can't be the seat of innumerable separate beings, or perhaps any particular subjective experiencer. You need not be a physicalist to reject this intuition; I gave examples which I thought were most friendly to functionalism.
"It seems conceivable to me. We know your brain already generates one mind. If you discovered that it generates another one, does that really seem like a square circle. I think it could be an infinite number, and I find that intuitively obvious."
This seems like a pretty weak reason to me; there are plenty of things that are logically impossible that I can "conceive" of in some sense, at least as convincingly (to me) as I can conceive of multiple consciousness--I can quite easily "conceive" that the one billionth digit of pi is 7, and indeed my imagination conjures up much richer, clearer scenarios of what that would mean than it does in the multiple-mind case. And yet, there is no possible world in which that's the case (the real digit is apparently 9).
Thus, I'm pretty skeptical about intuitive judgements about what is conceivable, especially in cases like consciousness where the phenomenon is not well understood. While it's true that ruling the idea out as inconceivable is already assuming physicalism, it seems to me asserting that it is conceivable is already assuming the falsity of physicalism.
I think the intuition provides enough ground to be wary about accepting physicalism, but it feels very up unjustified to me to start building a case on top of it.
The idea that there couldn't be "no fact of the matter" about whether you survive some surgery strikes me as really implausible. Just about every distinction you can think of--between night and day, war and peace, even between being pregnant and not being pregnant--admits of hard to classify, borderline cases that it's natural to describe as cases where there's no fact of the matter which side of the distinction we're on. The clearest counterexamples--eg, the distinction between even and odd numbers--concern abstracta. If the distinction between personal identity and non-identity doesn't admit any vague, borderline cases, that's really surprising!
I admit its hard to first-personally *imagine* borderline cases of personal identity, but that strikes me as telling us more about the activity of first-personal imagining (in particular, it's always from an imagined point of view) than the metaphysics of identity.
"I admit its hard to first-personally *imagine* borderline cases of personal identity"
After reading and rereading Parfit, meditating, and getting older and reading stuff I wrote years ago, it's not hard for me to imagine at all. The idea that "I"'m a single united self (since birth or shortly thereafter) seems like a useful socio-legal fiction.
Yeah I'm not quite sure how to put the point I want to concede, but then minimize the force if. Maybe something like, there's no good way to comply with the instruction: "imagine what is like to indeterminately survive." Cause then if I imagine *anything*, I'm imagining surviving.
But yeah I'm totally with you in thinking of personal identity as a highly non-fundamental, broadly forensic category. But I also suspect that's informed by my naturalism, so I don't want to put too much weight on it for fear of begging the question in this context.
I ought to point out that I'm profoundly aphantasic. Living as a perceptual minority, the idea that a normally color-sighted person's intuition that something couldn't be all red and all blue at the same time differs epistemologically from a synaesthete's intuition that a numeral can be written entirely in black ink and still have a color other than black, is much less automatic. Since the same goes for my (strongest of strong) intuition that the thought of a beach need not either have umbrellas or no umbrellas in it, which is apparently bizarre to over 95% of my fellow humans.
Evolutionary psychology seems to do a pretty good job of explaining the seeming of a socially embedded, persistent and indivisible self-identity. So I tend to accept this account over a doubling down on the truth of this particular weak seeming.
Seems like the first two arguments beg the question. The idea that we can create “someone else” with “identical physical and mental characteristics” seems more like a contradiction in terms than something that is ideally possible. Why is it possible? I don’t think you say.
Similarly, it seems like if there were “two” literally identical minds attached to the exact same body, there is really just one mind. Nothing changes. The assertion that two minds exist is ipse dixit, and dixit that has zero observable effects isn’t very credible.
As for the last argument, I would say that splitting brain hemispheres or just duplicating someone so the two halves share continuity would just be splitting the soul. The line of continuity branches. This is odd to some degree, but the oddness comes from the assumption that we can somehow split people’s minds perfectly.
The third argument (if successful) would only show that I *have* a soul, not that I *am* a soul. For all the personal identity argument shows, I might be identical to a body-soul composite, which has a soul as an essential part.
(1) It seems that Parfit's fission cases give us strong reason to reject the claim "iii. Identity is intrinsic, not extrinsic." *What matters* is intrinsic. But identity isn't, since we could survive as either Lefty or Righty, but only in the absence of the other.
(2) "it seems like two beings with identical mental lives can swap minds" -- this could be explained by co-consciousness relations. BrainA gives rise to qualiaA, and brainB qualiaB, but then at time t2 brainB generates qualiaB2, which is unified (in a larger, temporally extended experience) with qualiaA, rather than the qualiaB that we would normally have expected.
In general, you seem to be underestimating the resources available to bundle theorists to resist positing metaphysically heavyweight substances with haecceities (primitive identity facts). For example...
(3) "These would be different minds. Yet what would make them different?" The fact that they are two in number rather than one. They needn't differ at all in their *intrinsic* properties. It's just that we've imagined a scenario in which your brain gives rise to two bundles of qualia instead of just one. Once that's happened, nothing further is required to "make" the two minds numerically distinct. Compare: https://www.philosophyetc.net/2008/03/constituent-vs-world-ontology.html
1) I don't think Parfit gave us good reason to think that. If we're antecedently committed to the nonexistence of souls, then the lefty and righty case seems to show that it's non-intrinsic. But if we believe in souls we can naturally accommodate the intuition that there's a further fact about whether we survive. When one thinks about the lefty and righty case, it seems reasonable to ask "I know that my left brain will be in one hemisphere and my right brain in another, but will I still exist?"
2) But it seems incoherent for two things to trade properties if they have the same proper. This would be like supposing that my red shirt and my twins red shirt swap rednesses. What would this even mean?
I'm more broadly a bit skeptical of irreducible haecceities. Furthermore, it seems like souls are basically just haecceities for identity that continue over time--if you think there's a primitive fact that this is my consciousness and that continues over time, then that just sounds like what a soul is. But I think that the case where they swap now and then have different experiences shows that if there are irreducible haecceities, that continues over time.
3) Generally, we don't think that something can have two versions of the same property. My shirt doesn't have the property of red, and also a separate additional property of being red, distinct from the first property but not in regards to any of its qualities. If we accept the indiscernability of identicles, then they would have to differ in some way to be different, but how could they differ if they are identical in terms of both what's experienced and who is doing the experiencing. In other cases where primitive haecceities seem to make sense, like swapping identical atoms, they're not quite identical in that they don't share causal histories.
I think you're missing the force of the fission case. It seems that you are forced to deny claims like:
(a) You can expect to survive the destruction of your right hemisphere (assuming sufficient redundancy that your left hemisphere alone maintains very strong continuity and connectedness with your past self), if your left hemisphere is successfully transplanted into a new (very qualitatively similar) body.
(b) Likewise for the destruction of your left hemisphere, if the right lives on.
Instead, you seem committed to something like:
(c) whether you survive the destruction of a hemisphere and the transplant of the remainder of your brain into a new body depends upon the completely free-floating and unknowable fact of where your haecceity/soul resides. Since this is both intrinsic and unknowable, you should probably regard it as a coin flip whether you survive or not.
Also (going beyond fission cases to a general implication of soul views):
(d) In spectrum cases, a tiny incremental difference makes all the difference to whether you survive or not. It's prudentially rational to have 100% concern for all the different versions of you, up until that tiny difference makes the resulting person suddenly count as "not you", and then you should have 0% prudential concern for the resulting person -- a person who is qualitatively almost indistinguishable from someone who would have warranted 100% prudential concern.
I think (c) and (d) are independently much less plausible than (a) and (b)!
I also wonder what basis you have for thinking (e) is unlikely:
(e): Souls are constantly switching bodies, just without anyone noticing.
You can't appeal to induction, since we have no past observations of souls from which to predict their behavior. Maybe it's "simpler" to imagine that they (mostly) stay put? But that's a fairly weak reason. So it seems like you should give at least non-trivial credence to (e) if you accept a soul view. (Note that our qualia only give us access to qualitative aspects of experience. We cannot directly introspect on our haecceities to confirm whether or not we are the same person that we were a minute ago. So it really seems like we have ZERO observational evidence about identity facts. The notion that identity is stable over time is *purely* speculative.)
I think there are two senses of the word intrinsic. When we talk about it being intrinsic, it's not just whether external events can affect whether I exist. It's whether, without changing any feature of scenario A, event B can affect whether I'm around in scenario A. I think it can't--you probably survive just one hemisphere being destroyed, whichever it is. However, if one hemisphere is in each body, there's some contingent and hard to know fact about whether you survive. Note that what happens in the left hemisphere affects what happens to the right hemisphere, but it doesn't violate intrinsicness because it affects some feature of the right hemisphere, namely whether it gets the soul.
In regards to d, it seems you're linking of it the way a reductionist does. The soul theorist thinks there's a further fact about whether it's me beyond the mental changes. This fact might change if there are lots of mental changes. As a result, the reason lots of mental changes make a difference is because they cause a further fact to change--whether my soul stays latched on! It's not that a tiny difference is sufficient to change identity, it's that there are contingent laws that make tiny differences to my brain eventually make me stop being the same person.
In regards to e, I'd probably appeal to some combination of simplicity and phenomenal conservatism. Notably, I think the epiphenomenalist will have a similar puzzle explaining why we think that we're consistently conscious, rather than only conscious some of the time, and zombies other times. I also suspect that to remember something, it has to have happened to the same soul maybe, but I'm less sure about that.
Interesting! I'm curious to hear more about how you think about fission (versus Lefty-only brain transplantation), as a process. Should we be confident that you survive, but 50/50 about *which* person you survive *as*? Or is there a significant chance that the soul just pops out of existence if both hemispheres are successfully transplanted? Do you take any uncertainty here to be *purely* epistemic, or do you expect it to be a metaphysically chancy process?
What if the right hemisphere is cryonically preserved, while Lefty is transplanted? Do you still expect your soul to go with Lefty, or does it depend on future events (like whether Righty is ever unfrozen and successfully transplanted)?
What's the mechanism that determines all this uncertain soul-jumping? Are there idento-physical bridging laws, analogous to the property dualist's psycho-physical laws? Do physical objects get haecceities too (is there a real question as to the survival of the Ship of Theseus after all?), or just minds?
I'd be pretty uncertain about if lefty survives. I'd guess that whether lefty survives depends on what happens to righty, but if righty is frozen that probably wouldn't affect it. I think the uncertainty is epistemic and there are idento-physical bridging laws. I don't think that physical objects have haecceities--just minds. I think these considerations incline me more in the direction of a view like Goff's, according to which the explanation of features of the universe has something to do with the value of those features because it does seem like we've hit the jackpot in so many ways--fine-tuning, orderly psychophysical laws, and predictable soulcophysical laws.
> Reads this post around New Years when published
> "What in the devil's abstraction is this? Souls? Really?"
> Friend posts meme about forum post: "On building Omelas for shrimp; the implications of diversity-oriented theories of moral value on factory farming"
> Read's linked intro to Theory of Mind in the post
> Remembers arguments in this article
> Immediately convinced that soul theory is likely the best explanation of personal identity
I'm a soul man, do do do dooo do do do doooo. Happy New Year
I guess it just seems to me that the sorts of intuitions you're relying on here are the exact sort of intuitions we ought to doubt if naturalism is true - I see no particular reason why evolution would lead us to be able to have any sort of direct, unimpeachable insight into our own mental reality, and many reasons why such insight would even be negatively advantageous. Abandoning physicalism, which has been overwhelmingly successful in surviving many similarly structured challenges, and embracing an entirely new framework (one which seems unable, even in principle, to yield the sort of concrete empirical understanding physicalism at least anticipates) in response to these concerns seems obviously unwarranted to me. Why not just accept the idea that you might be wrong about whether two minds could exist alongside each other, or whether there is some further fact re: the experiencer? Especially since we know for a fact that human beings are capable of shedding such a sense in certain conditions?
To add to these great points: whatever intensity of intuition I've ever had supporting dualism was far weaker than many other intuitions I've rejected because of incompatibility with scientific findings and/or philosophical arguments. e.g. "The Earth is stationary and the sun moves across the top of it", "Different species are intrinsically distinct and unrelated to one another", "There could not be more permutations of a standard deck of cards than grains of sand in the Sahara". I'm not even convinced that I would have had an intuition that I was a separate substance ("soul") if I hadn't been taught it by a religious / Christian-influenced secular culture.
Very interesting. I share your intuition about the necessity of an experiencer, but I tend to be skeptical of those feelings. For your second argument: 1) I feel that the use of 'who' in point 3 assumes the conclusion; 2) if we run this argument about two identical red shirts, need we posit an essence of shirt that enables the shirts to differ?; relatedly 3) if you did in fact have two minds, there would necessarily be a physical difference for them both to be instantiated--otherwise point 1 is also assuming the conclusion.
For the second argument
1) well, they have to differ in some way. What way could they differ in regards to if they have the same experiences and are physically the same.
2) there couldn't be two different identical red shirts. What would that even mean? They couldn't be in the same location and physically identical or they'd be impossible to distinguish.
3) But it seems conceivable that I'd have two minds that are instantiated on the same physical substance.
1) This is right to my point. Could you run two identical software programs on the same hardware, using the very same bits? Can a hand perform two identical tasks at the same time, using the same materials? I don't know what motivates the notion that you could have two identical minds running on the same brain, being physically identical in every way but differing in who is doing the experiencing, unless you are already assuming some metaphysical weirdness, in which case the weirdness you're assuming is what informs the conclusion that two minds can share the same physical hardware.
2) I was talking about qualitative, not numerical identity.
3) That does not seem conceivable to me. I agree with Vikram, from whom I just learned the phrase ipse dixit (which has that lovely property of sounding like what it means).
I'm curious to probe your intuition here. Is there a limit to how many minds you think can be numerically identical save for the soul component? A thousand? An infinite number?
1) you are assuming physicalism, which I reject.
2) For two things to be numerically distinct they must differ in respect to some quality, if we accept the indiscernability of indenticals.
3) It seems conceivable to me. We know your brain already generates one mind. If you discovered that it generates another one, does that really seem like a square circle. I think it could be an infinite number, and I find that intuitively obvious.
Surely there are some constraints to your version dualism? It can't be that souls can be imputed wherever one likes. I give non-physicalism plenty of credence--I am usually a monist but not a physicalist--but if you want me to share in your intuition you should pump it a bit, maybe give some examples of other instances in which "two, or in fact any number, of identical things can share all physical properties, except an imperceptible essence." If there are none in your accounting, then more needs to be said about why. Actually, I could agree that we have souls on the basis of my own intuition that I have an inner experiencer of things, but disagree that I could have two identical ones. Could I not simply say that if they are identical in every way, they are the same mind? If you say 'no, there's a different who in mind #2' then we're back to the fact that you're assuming the who-ness. It also seems perfectly coherent to me that I could have a mind which is not physical, but which nonetheless can't be the seat of innumerable separate beings, or perhaps any particular subjective experiencer. You need not be a physicalist to reject this intuition; I gave examples which I thought were most friendly to functionalism.
"It seems conceivable to me. We know your brain already generates one mind. If you discovered that it generates another one, does that really seem like a square circle. I think it could be an infinite number, and I find that intuitively obvious."
This seems like a pretty weak reason to me; there are plenty of things that are logically impossible that I can "conceive" of in some sense, at least as convincingly (to me) as I can conceive of multiple consciousness--I can quite easily "conceive" that the one billionth digit of pi is 7, and indeed my imagination conjures up much richer, clearer scenarios of what that would mean than it does in the multiple-mind case. And yet, there is no possible world in which that's the case (the real digit is apparently 9).
Thus, I'm pretty skeptical about intuitive judgements about what is conceivable, especially in cases like consciousness where the phenomenon is not well understood. While it's true that ruling the idea out as inconceivable is already assuming physicalism, it seems to me asserting that it is conceivable is already assuming the falsity of physicalism.
I think the intuition provides enough ground to be wary about accepting physicalism, but it feels very up unjustified to me to start building a case on top of it.
The idea that there couldn't be "no fact of the matter" about whether you survive some surgery strikes me as really implausible. Just about every distinction you can think of--between night and day, war and peace, even between being pregnant and not being pregnant--admits of hard to classify, borderline cases that it's natural to describe as cases where there's no fact of the matter which side of the distinction we're on. The clearest counterexamples--eg, the distinction between even and odd numbers--concern abstracta. If the distinction between personal identity and non-identity doesn't admit any vague, borderline cases, that's really surprising!
I admit its hard to first-personally *imagine* borderline cases of personal identity, but that strikes me as telling us more about the activity of first-personal imagining (in particular, it's always from an imagined point of view) than the metaphysics of identity.
"I admit its hard to first-personally *imagine* borderline cases of personal identity"
After reading and rereading Parfit, meditating, and getting older and reading stuff I wrote years ago, it's not hard for me to imagine at all. The idea that "I"'m a single united self (since birth or shortly thereafter) seems like a useful socio-legal fiction.
Yeah I'm not quite sure how to put the point I want to concede, but then minimize the force if. Maybe something like, there's no good way to comply with the instruction: "imagine what is like to indeterminately survive." Cause then if I imagine *anything*, I'm imagining surviving.
But yeah I'm totally with you in thinking of personal identity as a highly non-fundamental, broadly forensic category. But I also suspect that's informed by my naturalism, so I don't want to put too much weight on it for fear of begging the question in this context.
I ought to point out that I'm profoundly aphantasic. Living as a perceptual minority, the idea that a normally color-sighted person's intuition that something couldn't be all red and all blue at the same time differs epistemologically from a synaesthete's intuition that a numeral can be written entirely in black ink and still have a color other than black, is much less automatic. Since the same goes for my (strongest of strong) intuition that the thought of a beach need not either have umbrellas or no umbrellas in it, which is apparently bizarre to over 95% of my fellow humans.
Evolutionary psychology seems to do a pretty good job of explaining the seeming of a socially embedded, persistent and indivisible self-identity. So I tend to accept this account over a doubling down on the truth of this particular weak seeming.
Seems like the first two arguments beg the question. The idea that we can create “someone else” with “identical physical and mental characteristics” seems more like a contradiction in terms than something that is ideally possible. Why is it possible? I don’t think you say.
Similarly, it seems like if there were “two” literally identical minds attached to the exact same body, there is really just one mind. Nothing changes. The assertion that two minds exist is ipse dixit, and dixit that has zero observable effects isn’t very credible.
As for the last argument, I would say that splitting brain hemispheres or just duplicating someone so the two halves share continuity would just be splitting the soul. The line of continuity branches. This is odd to some degree, but the oddness comes from the assumption that we can somehow split people’s minds perfectly.
They don't beg the question. They appeal to plausible intuitions. The fact that you reject a conclusion doesn't make it question begging.
I don't share your intuitions about two identical minds.
Your view of the last argument requires denying that identity is 1 to 1 and objective.
The third argument (if successful) would only show that I *have* a soul, not that I *am* a soul. For all the personal identity argument shows, I might be identical to a body-soul composite, which has a soul as an essential part.
Right. But I think you're just a soul because I don't think what I am can be vague, but my body is vague.
Interesting post! A few thoughts:
(1) It seems that Parfit's fission cases give us strong reason to reject the claim "iii. Identity is intrinsic, not extrinsic." *What matters* is intrinsic. But identity isn't, since we could survive as either Lefty or Righty, but only in the absence of the other.
(2) "it seems like two beings with identical mental lives can swap minds" -- this could be explained by co-consciousness relations. BrainA gives rise to qualiaA, and brainB qualiaB, but then at time t2 brainB generates qualiaB2, which is unified (in a larger, temporally extended experience) with qualiaA, rather than the qualiaB that we would normally have expected.
In general, you seem to be underestimating the resources available to bundle theorists to resist positing metaphysically heavyweight substances with haecceities (primitive identity facts). For example...
(3) "These would be different minds. Yet what would make them different?" The fact that they are two in number rather than one. They needn't differ at all in their *intrinsic* properties. It's just that we've imagined a scenario in which your brain gives rise to two bundles of qualia instead of just one. Once that's happened, nothing further is required to "make" the two minds numerically distinct. Compare: https://www.philosophyetc.net/2008/03/constituent-vs-world-ontology.html
Thanks for the reply.
1) I don't think Parfit gave us good reason to think that. If we're antecedently committed to the nonexistence of souls, then the lefty and righty case seems to show that it's non-intrinsic. But if we believe in souls we can naturally accommodate the intuition that there's a further fact about whether we survive. When one thinks about the lefty and righty case, it seems reasonable to ask "I know that my left brain will be in one hemisphere and my right brain in another, but will I still exist?"
2) But it seems incoherent for two things to trade properties if they have the same proper. This would be like supposing that my red shirt and my twins red shirt swap rednesses. What would this even mean?
I'm more broadly a bit skeptical of irreducible haecceities. Furthermore, it seems like souls are basically just haecceities for identity that continue over time--if you think there's a primitive fact that this is my consciousness and that continues over time, then that just sounds like what a soul is. But I think that the case where they swap now and then have different experiences shows that if there are irreducible haecceities, that continues over time.
3) Generally, we don't think that something can have two versions of the same property. My shirt doesn't have the property of red, and also a separate additional property of being red, distinct from the first property but not in regards to any of its qualities. If we accept the indiscernability of identicles, then they would have to differ in some way to be different, but how could they differ if they are identical in terms of both what's experienced and who is doing the experiencing. In other cases where primitive haecceities seem to make sense, like swapping identical atoms, they're not quite identical in that they don't share causal histories.
I think you're missing the force of the fission case. It seems that you are forced to deny claims like:
(a) You can expect to survive the destruction of your right hemisphere (assuming sufficient redundancy that your left hemisphere alone maintains very strong continuity and connectedness with your past self), if your left hemisphere is successfully transplanted into a new (very qualitatively similar) body.
(b) Likewise for the destruction of your left hemisphere, if the right lives on.
Instead, you seem committed to something like:
(c) whether you survive the destruction of a hemisphere and the transplant of the remainder of your brain into a new body depends upon the completely free-floating and unknowable fact of where your haecceity/soul resides. Since this is both intrinsic and unknowable, you should probably regard it as a coin flip whether you survive or not.
Also (going beyond fission cases to a general implication of soul views):
(d) In spectrum cases, a tiny incremental difference makes all the difference to whether you survive or not. It's prudentially rational to have 100% concern for all the different versions of you, up until that tiny difference makes the resulting person suddenly count as "not you", and then you should have 0% prudential concern for the resulting person -- a person who is qualitatively almost indistinguishable from someone who would have warranted 100% prudential concern.
I think (c) and (d) are independently much less plausible than (a) and (b)!
I also wonder what basis you have for thinking (e) is unlikely:
(e): Souls are constantly switching bodies, just without anyone noticing.
You can't appeal to induction, since we have no past observations of souls from which to predict their behavior. Maybe it's "simpler" to imagine that they (mostly) stay put? But that's a fairly weak reason. So it seems like you should give at least non-trivial credence to (e) if you accept a soul view. (Note that our qualia only give us access to qualitative aspects of experience. We cannot directly introspect on our haecceities to confirm whether or not we are the same person that we were a minute ago. So it really seems like we have ZERO observational evidence about identity facts. The notion that identity is stable over time is *purely* speculative.)
I think there are two senses of the word intrinsic. When we talk about it being intrinsic, it's not just whether external events can affect whether I exist. It's whether, without changing any feature of scenario A, event B can affect whether I'm around in scenario A. I think it can't--you probably survive just one hemisphere being destroyed, whichever it is. However, if one hemisphere is in each body, there's some contingent and hard to know fact about whether you survive. Note that what happens in the left hemisphere affects what happens to the right hemisphere, but it doesn't violate intrinsicness because it affects some feature of the right hemisphere, namely whether it gets the soul.
In regards to d, it seems you're linking of it the way a reductionist does. The soul theorist thinks there's a further fact about whether it's me beyond the mental changes. This fact might change if there are lots of mental changes. As a result, the reason lots of mental changes make a difference is because they cause a further fact to change--whether my soul stays latched on! It's not that a tiny difference is sufficient to change identity, it's that there are contingent laws that make tiny differences to my brain eventually make me stop being the same person.
In regards to e, I'd probably appeal to some combination of simplicity and phenomenal conservatism. Notably, I think the epiphenomenalist will have a similar puzzle explaining why we think that we're consistently conscious, rather than only conscious some of the time, and zombies other times. I also suspect that to remember something, it has to have happened to the same soul maybe, but I'm less sure about that.
Interesting! I'm curious to hear more about how you think about fission (versus Lefty-only brain transplantation), as a process. Should we be confident that you survive, but 50/50 about *which* person you survive *as*? Or is there a significant chance that the soul just pops out of existence if both hemispheres are successfully transplanted? Do you take any uncertainty here to be *purely* epistemic, or do you expect it to be a metaphysically chancy process?
What if the right hemisphere is cryonically preserved, while Lefty is transplanted? Do you still expect your soul to go with Lefty, or does it depend on future events (like whether Righty is ever unfrozen and successfully transplanted)?
What's the mechanism that determines all this uncertain soul-jumping? Are there idento-physical bridging laws, analogous to the property dualist's psycho-physical laws? Do physical objects get haecceities too (is there a real question as to the survival of the Ship of Theseus after all?), or just minds?
I'd be pretty uncertain about if lefty survives. I'd guess that whether lefty survives depends on what happens to righty, but if righty is frozen that probably wouldn't affect it. I think the uncertainty is epistemic and there are idento-physical bridging laws. I don't think that physical objects have haecceities--just minds. I think these considerations incline me more in the direction of a view like Goff's, according to which the explanation of features of the universe has something to do with the value of those features because it does seem like we've hit the jackpot in so many ways--fine-tuning, orderly psychophysical laws, and predictable soulcophysical laws.