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Tuesday, May 27, 2008

The Ship of Jason

In response to the responses to Bob's query about what our readers want us to write about -- and here I thought I started a blog so that I could write about whatever the heck I wanted to! -- I post a genuine philosophical puzzle, and one which I really don't know how to answer.

The paradigmatic example of the conundrum is 'the ship of Jason' (of Argonaut fame). Suppose at time x we can uncontroversially identify ship A as 'the ship of Jason'. But time passes. Gradually the Argonauts and their successors replace more and more components of the ship with newer instances of the same part. Finally, the day comes when every single bit of ship A that made it up at time x is gone. Is the vessel in question still the ship of Jason?

Next, let us imagine that someone scavenges all of the discarded pieces of the ship that had comprised it at time x, and uses them to assemble a second, perhaps somewhat decrepit, ship, and at time y proclaims 'Behold the ship of Jason'! If you decided that the totally refurbished ship introduced in the previous paragraph was still 'the ship of Jason', then what do you make of this new claimant to the designation? It, after all, is made up of precisely the same components as the ship that we agreed clearly was the ship of Jason at time x. It seems an abuse of common usage to hold that at time y there exist two ships of Jason, even though Jason himself had but one while he was alive. Nevertheless, we have at hand a pair of craft either of which, in the absence of the other, we would probably regard as sensibly designated 'the ship of Jason'. So how to resolve the embarrassment of there being two such vessels?

The puzzle does not, of course, only arise with regards to inanimate objects, and the problems to be solved by any philosophical analysis of person-hood are probably readily apparent. If you happen to be a materialist who still posits the real existence of individual human agents, then you are tasked with explaining why you are justified in talking about the 'same' person across a lifetime when that 'individual' at 70 is composed of entirely different bits of matter than she was at 10. If, on the ohter hand, you contend that there is some constant spiritual essence animating and uniting all of the diverse physical manifestations of 'an individual', then you face the difficulty of explaining how such an immutable entity can have any connection whatsoever with the ever-changing attributes of people as we un-philosophically experience our acquaintances in day-to-day life. At least at first glance, such an eternal absolute would seem to be categorically immune from being effected by temporal happenings, just as the Pythagorean Theorem is not impacted by the outcome of a war or the results from an election. Quite to the contrary, our 'folk' understanding of our fellow humans conceives them as continually transforming per the influence of new experiences. However, if that picture is mostly correct, then where is the enduring 'person' whom we are inclined, for instance, to hold responsible for a crime? If 'Joe 2008' contends he is 'a whole new man' from 'Joe 2007' who committed a murder, then, absent any plausible notion of how they are really still the 'same individual', how can we justify punishing 'Joe 2008' for a transgression of 'Joe 2007'.

6 comments:

  1. I happen to be a materialist who still posits the real existence of individual human agents, and I feel justified in talking about the 'same' person across a lifetime, because I identify the person with their stream of consciousness, not just their body parts. Just as I identify the software Windows 95 by its code, and not by whether it is encoded on to CD, floppy disk, or some other physical medium.

    If we ever become able to "upload" a person's consciousness onto a new physical medium, this might raise interesting questions, such as what it would mean if we uploaded more than one copy of the same consciousness onto two or more physical mediums. Would there be multiples of me running around?

    On a semi-related note, I've always appreciated this Otto Neurath quote:

    "We are like sailors who on the open sea must reconstruct their ship but are never able to start afresh from the bottom. Where a beam is taken away a new one must at once be put there, and for this the rest of the ship is used as support. In this way, by using the old beams and driftwood the ship can be shaped entirely anew, but only by gradual reconstruction."

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  2. I don't have any real answers, but I humbly suggest that you first tackle the problem as it relates to Jason's ship. Then once you are confident you understand how it works on that example, then you can try tackling personhood.

    But as it is, I think you are saying something like, "Hey kids, it's multiplication time! What is 4.6 times ten million? And now, before you answer, let me also say that it is close to the number fetuses aborted since Roe v. Wade. So let's think about that too."

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  3. Micha,

    FYI I answered you in two threads that have moved down the chute. Maybe you saw them and didn't have anything else to say, but I just wanted to alert you to them. One was about the personalism one I think, where you kept saying "Meh." And shoot, I can't remember the other one at the moment. Hopefully you can remember where we were arguing.

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  4. "I feel justified in talking about the 'same' person across a lifetime, because I identify the person with their stream of consciousness, not just their body parts..."

    I don't think 'stream of consciousness' buys you anything here -- instead, it's just a different way of asserting 'That's one individual'. I say this because there certainly is no 'stream' in the sense of something displaying unbroken continuity, e.g., we fall asleep, we pass out, we forget things, we have 'memories' of things that never happened. Why not claim, for instance, that it is 'one' person for each 'bout' of consciousness, but a new one for each separate bout?

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  5. Gene,

    Yup, I actually had the same worry about interruptions to the stream of consciousness in my post responding to your "self-ownership" argument.

    To wit,

    "But what does it mean to have the same mind (even if we grant different physical implementations of brains) at time t1 and t2? I do not have the same thoughts, perceptions, memories, emotions, will and imagination that I had 20 years ago. Am I a completely seperate person from my past self? Maybe the persistence of mind over time is achieved through a single stream of consciousness. We might even grant that this single stream of consciousness can tolerate interruption through sleep or coma and yet still be considered the same stream of consciousness--the same person--upon waking up. But what about an amnesiac, whose consciousness is completely different after suffering from a brain injury? Can we still say this is the same stream of consciousness? Is it really the same person before and after the amnesia, if there is a total loss or change of memory, personality, emotion, perception and thought?"

    Nevertheless, this is about as close as I can come to defining personhood. At certain extremes, like in a case of complete amnesia, there is a very real sense that this isn't the same person as before. And there are some contexts in which it's useful to think of me at time t1 and me at time t2 as two separate persons.

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