"The Heart Sutra" is one of the most famous Buddhist texts, traditionally regarded as a potent expression of emptiness and of Buddha's perfect wisdom. This book explores the elaborate philosophical and ritual uses of "The Heart Sutra" in India, Tibet and the West. It includes full translations of the eight extant Indian commentaries, and translations of six essays that examine the unusual roles that "The Heart Sutra" has played - as a mantra, an exorcism text, a tantric meditation guide and material for comparative philosophy. The translations, taken together, demonstrate why commentary is as central to modern scholars on Buddhism as it was for Buddhists in ancient times.