Argument for the mind from continuity of identity despite change
Hey guys! I heard this really really interesting argument just recently on the debate website I'm on. It got me thinking, and it seems pretty strong. Let me know what you think.
"1. If all we are is the sum of our physical parts, then we do not maintain personal identity through physical change.
2. We do maintain personal identity through physical change.
3. Therefore, we are not merely the sum of our physical parts.
Suppose there is a wooden ship, and we replace each piece of wood on the ship one at a time until there are no original pieces of wood left, and the entire ship is made of new wood. If that happened, then you would no longer have the original ship. It would be a completely different ship.
If you are not persuaded, let's press the analogy further. Let's say that we gather together the original wood that used to be part of the ship, and we assemble it into a ship that has all of the properties of the original ship before you started replacing parts. Now you've got two ships--one made entirely of new parts, and one made of all the original parts. Surely if either of these ships stand a chance of being the original, it's the one with the original parts.
If you are still not persuaded, let's tweak the thought experiment a little. Instead of replacing each piece of wood with another piece of wood, let's say we replace each piece of wood with cardboard. In the end, we'd have a ship made entirely of cardboard. By now, you should be able to see that if you replace all the parts on the ship, then you no longer have the original ship.
So it is with people. We are in a constant state of change, and within 10 to 15 years, we have a mostly new body. If we were identical with our bodies (i.e. if we are our bodies), then none of us have been around for longer than 10 or 15 years. You yourself never were a baby. Even some of the memories you have were not your own. Rather, you inherited them from somebody else who had those experiences but has passed out of existence.
But to deny that we ourselves have continued to exist in spite of our physical changes is absurd, and many counter-intuitive results follow from it. It would follow that nobody should be convicted of a crime that happened more than 15 years earlier. It would follow that you were never born and that you have no parents. It would follow that your memories are not your own. It would follow that within another 15 years, you could cease to exist without dying.
Since we do maintain personal identity through physical change, it follows that we are not identical with our bodies. We are immaterial, and we animate different bodies throughout our lives." 
The argument is a valid modus tollens syllogism, so if the premises are true, the conclusion follows necessarily. The first premise seems to be obviously true, and I doubt anyone would want to deny the second premise. I suppose that's probably what people would do nowadays.. Although it kindof goes to show how contra common sense the materlialist position really is.
  "Your Amazing Regenerating Body" by Gaia Vince http://www.newscientist.com/article/mg19025561.900-your-amazing-regenerating-body.html
"Cells That Last a Lifetime" by April Holladay http://usatoday30.usatoday.com/tech/columnist/aprilholladay/2007-03-30-cell-lifetime_N.htm
, User:philochristos, URL: http://www.debate.org/debates/That-the-mind-is-a-purely-physical-substance./1/