Such was the basic form of Buddhism as practiced for almost eight hundred years—until, that is, Nagarjuna, who began paying attention to this strange duality between samsara and nirvana. For Nagarjuna, this duality tore Reality in half and didn’t produce liberation but subtle illusion. For him, there is no ontological difference between samsara and nirvana. The difference is merely epistemological. That is, Reality looked at through concepts and categories appears as samsara, while the very same Reality looked at free of concepts and categories is nirvana. Samsara and nirvana are thus not-two, or “nondual.” And this caused a major revolution in Buddhist thought and practice.
Gautama Buddha had discovered the “emptiness,” or ultimately illusory nature of, the separate-self sense; but he had not discovered the emptiness—the shunyata—of all of what is usually called “reality” (including not only all subjects, or selves, but all objects, or “dharmas”). Buddhism had just taken its second major Turn in its illustrious history, adding a novel and profound element to its already accepted discoveries.
