@Invisible: The river does not have a conscience, it is pure matter. We are no only matter, our conscience does not change if we get a kidney transplant. It is a change, but not an essential one.
@Invisible: I don't think we are totally the same we were a second ago. I would not call that person a different one, since he can think all the same. However, if braon transplant was possible, someone would be a different person when receiving a new brain.
