One thousand years ago, Gampopa, the illustrious heart son of Tibet's great yogin Milarepa, essentialized the entire Buddhist path in a concise set of pith instructions that became known as the Four Dharmas of Gampopa. Since that time, this profound teaching has been used by many eminent masters as a vehicle for imparting the key points of Buddhist practice, including, in the fourteenth century, the incomparable Longchenpa, whose brilliant exposition...