Consider yourself. I want you to imagine a scene from your childhood. Pick something evocative.. Something you can remember clearly, something you can see, feel, maybe even smell, as if you were really there. After all, you really were there at the time, weren't you? How else would you remember it? But here is the bombshell: you WEREN'T there. Not a single atom that is in your body today was there when that event took place. Every bit of you has been replaced many times over.. The point is that you are like a cloud: something that persists over long periods, whilse simultaneously being in flux. Matter flows from place to place and momentarily comes together to be you. Whatever you are, therefore, you are not the stuff of which you are made.