QUOTE : If any atom of your body was gradually replaced by a new one, would you still be the same person? Or, to put it another way, if all the atoms in your body were gradually thrown out of your body, and then all these atoms were assembled in the new system to construct an artificial devise -- a 'humanoid robot', what would distinguish you, at an earlier time, from this robot, at a later time? To understand your personal identity over time, think over these questions above.