Thursday, November 08, 2007

Is Non-reductionism about Identity Possible?

I agree with most of what Parfit says about personal identity. But I'm skeptical of one claim he makes. He suggests that he might have been wrong -- that although in fact reductionism is true, and personal identity is not a further fact over and above physical and psychological continuity, things could have turned out otherwise.

Parfit thinks that persons could have been irreducible Cartesian Pure Egos, spiritual substances whose continued existence is all or nothing. Possible evidence for this would be provided by apparent reincarnation, i.e. if someone had apparently accurate memories/knowledge about the life of someone long dead, which they could not have learned by natural means. This would be evidence that we are spiritual substances. And if we found that we could not induce intermediate degrees of psychological continuity -- say that brain damage either left you completely unaltered or a completely different person, with nothing in between -- then that might be evidence that the continued existence of the ego is all-or-nothing, and does not admit of vagueness or borderline cases.

Even granting all this, is it non-reductionism? Or does it instead show that rather than just being reducible to physical stuff and psychological continuity, our personal identity may instead have had a slightly different (soul-stuff based) reduction basis? I'm not seeing any significant difference here. Suppose that (1) our psychological traits inhere in a spiritual substance or 'ego' that exists independently of, but interacts with, the physical; and (2) these psychological traits are not susceptible to incremental change or manipulation -- their persistence is "all or nothing". What then? It does not seem to follow that (3) the ego endures rather than perdures, nor (4) each ego has a haecceity or essentially unique property or 'thisness' which fixes its identity as a further fact over and above the qualitative facts.

If identity is a 'deep further fact', one of the fundamental base facts from which all other truths may be derived, then it should vary independently from, rather than supervening upon, the other fundamental facts. (Shouldn't it?) There must be two possible worlds which are exactly similar but which vary in the identity facts -- perhaps due to switched haecceities. That seems a bit nutty, which is why we should be reductionists about identity in general. But note that adding spiritual substances of limited qualitative repertoire into the world doesn't seem to change this in the slightest. We can still think it an empty question whether the corresponding egos in two possible worlds are numerically identical or merely exactly similar. We can still think that the identities of the various egos in the world reduce to qualitative facts about what the world is like (there is some soul-stuff over here, housing such-and-such a personality).

Consider (apparent) reincarnation. What makes your ego "one and the same" as that of a Japanese woman who lived a thousand years ago? Presumably, this identity fact is reducible to the psychological continuity and counterfactual dependence that holds between you. That is, you have her memories etc., and this involves a kind of robust tracking such that if she had lived differently then you would now have appropriately different memories (etc.) in their place. It is this which inspires us to combine the various temporal parts into a single, unified ego (without it seeming objectionably gerrymandered). There is no 'further fact' in the sense of haecceities or other special identity facts. We have simply imagined a scenario where there are some further qualitative facts which go beyond the sorts of substances and connections that are actually found in our world. I see nothing here for the non-reductionist to get excited about. Am I missing something?


  1. Richard,

    This argument seems to be assuming that the basic objects are time-slices. If this is so, wouldn't our account of the identity of anything over time be reductionist?

    I take it a non-reductionist about personal identity is already assuming that there are objects that endure over time. In this case, wouldn't the continuous existence of an ego over time be like the continuous exsitence of my couch over time? So long as a particular ego never loses any of its essential features, wouldn't that be enough for it to endure?

    You seem to know this literature much better than I do, so I'm genuinely curious about the problem here.

  2. "This argument seems to be assuming that the basic objects are time-slices. If this is so, wouldn't our account of the identity of anything over time be reductionist?"

    Yeah, that's what I was thinking too. What puzzled me, then, is that Parfit seems to think that reductionism is merely contingently true, even though he doesn't give any reason to think that it's merely contingent that the basic objects are time-slices. He explains how there might have existed Cartesian egos, but why think that their manner of persistence through time would be any different in kind from your couch's (which, we reductionists assume, perdures rather than endures)?

  3. I can see that making sense from an ultra-Quinean perspective, kind of.
    Parfit can be construed as giving an account of the empirical conditions needed for a Cartesian conception of personhood to never run into any unsolvable dillemas in its application [as long as you don't do any conditional conceptual analysis, which is unwelcome from a Quinean perspective anyway].

    When joined by a certain kind of anti-realism about philosophical truths this can make for contingent reductionism: Given that Cartesian personhood seems to be our default conception of personal identity, and given the remarkable correlation between emirical discoveries that make it inapplicable and the revealation of its a-priori incoherence, personal identity seems like a prime candidate for contingency from a Quinean point of view.

  4. Maybe a good analogy is a philosopher claiming that platonic realism about morality would make more sense if our world was Middle Earth.

    I don't think that line of reasoning ultimately works, but it has some attractive qualities.

  5. I always thought that Parfit's argument was meant to prove something specific about personal identity. One way personal identity would be reducible: basic objects are time slices. But then the identity of everything is reducible. So maybe Parfit is assuming some objects do endure, but trying to show something special about P.I. Even in a world with enduring objects, the self can't be one of those objects.

  6. Ah, that would make more sense -- thanks!

  7. I take identity over time to be primitive. Does that make me a non-reductionist?

  8. Sure. (At least, I'm not sure what it would mean to take something as primitive and yet deny that it's a "further fact" beyond the various kinds of qualitative continuity.)

  9. The seeming ad-hoc nature of the 'no branching clause' in various reductionist accounts of personal identity has always struck me as philosophically unsatisfying.

    Why isn't it more reasonable (perhaps since our concepts of diachronic identity are on firmer ground than revisionist accounts like Parfit's), then, to interpret Parfit's fission-style arguments in favor of reductionism as instead a kind of reductio, where the absurdity of having two or more 'survivors' all satisfy the criterion is itself taken to show the inadequacy of reductionist criteria of identity over time?

    Identity over time is a 'further fact', but it's not a mysterious further fact in the way that a Cartesian soul or a Lockean consciousness (understood as possibly immaterial) would be, it's a further fact simply because identity over time is primitive and so unanalyzable.


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