Who am I?

Clear cold weather. No planes or animals. But my mind did start to wander and wonder. What is it that makes me? My heart? My brain? My liver? What is it that if removed would no longer be me? But it's to philosophical to answer. Last week an unnamed reader returned a book I had lent him about String Theory. Couldn't be proven, too philosophical not enough Science.
In 1980 a book was written which suggested the universe, as we experience it, is in reality a giant holograph. In which case any single part 'knows' the content of the entire holograph albeit in lesser definition. But the author did explain a lot of psychic events which could be measurable if you believe). When you come right down to it, it's all about belief.
String Theory, Hologram... both prove that we're all on this flight together.
Dick