"How can we validate the existence of spiritual realities - ""specifically,"" the mystical experiences claimed by the world's wisdom traditions - in the face of modern and postmodern attacks that deny those realities as unscientific or reduce them to social constructions? In his most cutting-edge work on religion since The Marriage of Sense & Soul ""(1998),"" Wilber applies his acclaimed integral approach to formulate a theory of spirituality that honors the revolutions in science and culture while incorporating the legacy of the great religions."