Let me ask you a few simple questions: Do you exist at this moment? Did you exist five years ago? Are you your body? Most people would answer "yes" to all three questions. But if you identify your body as yourself, and simultaneously accept that you exist now and also existed five years ago, then you have a problem: The body you had five years ago does not exist today. There is a dynamic turnover of atoms and molecules which make up your body. There isn't a single particle of matter — not one atom — present in your body today that was present five years ago. The body you have today is not the same body you had five years ago. It's not that the body you had still exists but has now changed somewhat. No. The body you had is gone. That collection of atoms appearing as flesh, bone, blood, hair, and so on no longer exists. Yet you still exist.

~ Chris Butler (Jagad Guru Siddhaswarupananda Paramahamsa)
Science of Identity Foundation