The Spectrum of
by Ken Wilber
Wilber's groundbreaking synthesis of religion, philosophy, physics, and psychology started a revolution in transpersonal psychology.
He was the first to suggest in a systematic way that the great psychological systems of the West could be integrated with the noble contemplative traditions of the East.
Spectrum of Consciousness, first released by Quest in 1977, has been the prominent reference point for all subsequent attempts at integrating psychology and spirituality.