"Know thyself," is inscribed in stone at the entrance to the Temple of Apollo at Delphi. For Socrates, "The unexamined life is not worth living." Plato likens us to one spending life chained in a dark cave. It seems that some people, living two or three thousand years ago, had discovered something. They had opened the door to something they regarded as having the highest value some insight that makes life worth living. What is it they came to know? That is the sole subject of this book. What they knew, and, more importantly, how we can come to know what is so enriching. Some insight to start...