[NetBehaviour] Free Will and Identity.

marc garrett marc.garrett at furtherfield.org
Wed Nov 7 02:10:41 CET 2007

Free Will and Identity.

Identity: who am I?

Every year 98% of the atoms of my body are replaced: how can I claim to 
be still the same person that I was last year, or, worse, ten years ago? 
What is (where lies) my identity? What is "my" relationship to the 
metabolism of my body?

Derek Parfit once proposed a thought problem: what happens to a person 
who is destroyed by a scanner in London and rebuilt cell by cell in New 
York by a replicator that has received infinitely detailed information 
from the scanner about the state of each single cell, including all of 
the person's memories? Is the person still the same person? Or did the 
person die in London? What makes a person such a person: bodily or 
psychological continuity? If a person's matter is replaced cell by cell 
with equivalent cells is the person still the same person? If a person's 
psychological state (memory, beliefs, emotions and everything) is 
replaced with an equivalent psychological state is the person still the 
same person? The question eventually asks what is "a life": is it a 
continuum of bodily states, whereby one grows from a child to an adult, 
or is it a continuum of psychological states? Or both? Or none?

The most obvious paradox is: how can reality be still the same as we 
grow up? Do two completely different brains see the same image when they 
are presented with the same object? If the brains are different, then 
the pattern of neural excitement created by seeing that object will be 
completely different in the two brains. How can two completely different 
brains yield the same image in the two brains? The logical conclusion is 
"no, the tree I see is not the tree you see, we just happen to refer to 
it the same way so it is not important what exactly we see when we look 
at it". But then how can we see the same image yesterday, today and 
tomorrow? Our brain changes all the time. Between my brain of when I was 
five years old and my brain of today there is probably nothing in 
common: every single cell has changed, connections have changed, the 
physical shape of the brain has changed. The same object causes a 
different pattern in my brain today than it did in my brain forty years 
ago. Those are two different brains, made of different cells, organized 
in different ways: the two patterns are physically different. 
Nonetheless, it appears to me that my toys still look the same. But they 
shouldn't: since my brain changed, and the pattern they generate has 
changed, what I see today should be a different image than the one I saw 
as a five-year old. How is it that I see the same thing even if I have a 
different brain?


More information about the NetBehaviour mailing list