On Tue, May 30, 2006 at 03:02:05PM -0700, "Hal Finney" wrote:
> One way (perhaps the only way) I could see to do it would be for you
> to gradually acquire amnesia, then once you have forgotten your past,
> your personality could gradually change to match Napoleon's, then you
> could gradually recover memory of Napoleon's past.

Yes - I think this is roughly equivalent to the regression to embryo
process I suggested before.

> Whether such an extreme case would still support whatever conclusions
> Parfit seeks to draw, I don't know.  You're never half-yourself and
> half-Napoleon.  Rather, you sort of stop being anybody in the middle
> of the process.  I don't think it makes any sense to suppose that you
> could be half-yourself and half-Napoleon.

My reading of Parfit was that half-yourself/half-napoleon states were
required. Perhaps others more familiar with Parfit can comment.

> Certainly the physical process Russell quoted could never work,
> because there is no one-to-one correspondence between the neutrons in
> your brain and Napoleons.  And each neutron has a distinctive shape.
> If you brought it over unchanged, it would intersect with and overlap
> other cells in the brain, and be non-functional.  But if you change its
> shape, it won't be the same neuron in terms of its functional behavior.
> If you brought neurons over from Napoleon's brain but altered them
> in the process to match your own neurons physically and functionally,
> then you would never stop being yourself.
> Hal Finney

I'm not sure shape of neurons is sufficient - we can suppose (for the
sake of argument) that nanoscale wires are connected between neurons
on Napoleon's brain and your own, and that once in place, the
neurosurgeon just needs to activate the links 1 by 1 (all 10 billion
of them).

My objection was that there will not be a one-to-one correspondence
between neurons in the two brains. Napoleon probably has a Josephine
neuron that I don't have and so on. So even switching over neurons
will not give half-half states. Instead when the Josephine neuron is
connected to my brain it will probably have some other
function. Indeed as I argue, the most likely result is non-function.

A more likely scenario is that whole modules are swapped at a
time. The human brain is quite modular, a part dedicated to processing
vision, another for smell, another to control the left arm and so
on. Swapping whole modules (assuming sufficient technological prowess)
could well lead to functioning hybrid brains. However the resulting
"in-between" brains do not lie on a spectrum, as is needed for
Parfit's argument. The result is a distinct person in each step. Some
versions may result in split persons, by analogy with the split brain
case - ie if we constructed a brain with my right hemisphere and
Napoleon's left, and left out the connections in between.


A/Prof Russell Standish                  Phone 8308 3119 (mobile)
Mathematics                                    0425 253119 (")
UNSW SYDNEY 2052                         [EMAIL PROTECTED]             
Australia                                http://parallel.hpc.unsw.edu.au/rks
            International prefix  +612, Interstate prefix 02

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