This simple truth—that the control of consciousness determines the quality of life—has been known for a long time; in fact, for as long as human records exist. The oracle’s advice in ancient Delphi, “Know thyself,” implied it. It was clearly recognized by Aristotle, whose notion of the “virtuous activity of the soul” in many ways prefigures the argument of this book, and it was developed by the Stoic philosophers in classical antiquity. The Christian monastic orders perfected various methods for learning how to channel thoughts and desires.
