Tathagatagarbha -- Buddha Nature -- is a central concept of Mahayana Buddhism crucial to all the living practice traditions of Tibetan and Zen Buddhism. Its relationship to the concept of emptiness has been a subject of controversy for seven hundred years. Dr. Hookam's work investigates the divergent interpretations of these concepts and the way the Tibetan tradition is resolving them. In particular she does this with reference to the only surviving Indian commentary on the Tathagatagarbha doctrine, the Ratnagotravibhaga. This text addresses itself directly to the issue of how to relate the doctrine of emptiness (the illusory nature of the world) to that of the truly existing, changeless Absolute (the Buddha Nature). This is the first work by a Western writer to present an analysis of the Shentong tradition based on previously untranslated sources. The Shentong view rests on meditative experience that is inaccessible to the conceptualizing mind. It is deeply rooted in the sutra tradition of Indian Buddhism and is central to an understanding of the Mahamudra and Dzogchen traditions and Tantric practice among Kagyupas and Hyingmapas.