" All known great religions have had an exoteric aspect, that is, exterior, profane, for the masses of believers, and another esoteric, for a restricted select minority of initiates. So it was with the Egyptian and Greek cults. Those ignorant people who pompously speak to us about Aristotle, Socrates, Plato and the 'rational thought of the Greeks' ignore the fact that behind their ideas one finds the Eleusinian Mysteries of Delphi and elsewhere, in which these same philosophers, above all Plato, Aeschylus, Euripides took part, though they could not speak of it in public. The Orphic cults and mythology are the foundation of the philosophical thought of Ancient Greece. The word esoteric itself comes from the Greek work eisoteo and means 'to enter into' and 'to open a door' (towards the Gods: Theo, eiso-theo). "

― Miguel Serrano