The Problem of Myself 2

Friend and intrepid reader Miranda raised some questions about my earlier post on the problem of self-identity. 

I am struggling with the idea that an identical twin might be closer to being the same individual than two people who shared the same memories. Your suggestion makes me think of Abigail and Brittany Hensel, conjoined twins who share a body, but who are, nevertheless, very distinct people. Their personalities quite different, with one girl being more extroverted than the other. I think it would be a mistake to think that the fact that the two share most of their limbs and, of course, DNA, meant that they were not two separate individuals. 

I think that this raises a lot of interesting questions, some of which I will address now. 

I do not hold that twins, identical, conjoined, or otherwise, are in any significant sense the same person.  They are no more the same person than two distantly related strangers; or at least that is true past a certain point in development. 

If you hold that personhood begins at conception (as I do), then identical twins were at some stage precisely the same person.  Then that person split into two.  To escape that conclusion, one would have to adopt a more or less medieval view of ontogeny, with a soul flying into the womb after the biological process was underway.  I am not convinced that any such view is coherent. 

If consciousness depends on a functioning nervous system, then I assume that any such division occurs prior to the emergence of consciousness.  This would be the major difference between me and a clone produced by one of my cells.  There is no question of whether the undivided zygote will “wake up” in either or both embryos since it isn’t awake yet.  Existential continuity will begin after two separate individuals have emerged. 

Miranda goes on to note this:

I also think that if a man were to receive multiple transplants and thus was made up of parts that originated from different DNA than his original parts had come from he would still be the same individual as he had been before.

This is the famous “ship of Theseus” problem.  The ship that Theseus rode back to Athens after he slew the Minotaur was preserved in that city (according to legend).  Over time parts of it were replaced as it weathered.  Eventually all the original parts had been replaced.  Is it still the same ship?  I say yes.  At every point in its history, new parts were integrated into old ones according to the original form.  That continuity of replacement grounds identity in the ship just as it does in us.  Our parts are being constantly replaced with new cells and materials.  Over the course of a single lifetime, all the material constituents are replaced about three times.  Yet I seem to be the same boat I was at birth. 

Finally:

But I am not sure what measure the amount of individuality in a person can be measured. How would you measure it? I look forward to reading more about the continuity of expected futures problem, should you choose to write about it in the future.

I look forward to that as well, for right now I have no idea what I will say.  It seems to me that individuality is not a matter of degree.  I will either have to bear the burdens and get to reap the benefits of my life tomorrow or not.  That will be true regardless of how many parts have been replaced.  I am pretty sure that if I am cloned and my memories downloaded to KB2 I will not taste his breakfast.  I remain convinced that my existential continuity is grounded in this embodied mind.  Beyond that, I am at a loss.  All modern philosophy turns on the mind/body problem.  Consciousness is indeed the hard problem.