Book excerpt: The Heart Sutra is perhaps the most famous Buddhist text, traditionally regarded as a potent expression of emptiness and of the Buddha's perfect wisdom. This brief, seemingly simple work was the subject of more commentaries in Asia than any other sutra. In Elaborations on Emptiness, Donald Lopez explores for the first time the elaborate philosophical and ritual uses of the Heart Sutra in India, Tibet, and the West. Included here are full translations of the eight extant Indian commentaries. Interspersed with the translations are six essays that examine the unusual roles the Heart Sutra has played: it has been used as a mantra, an exorcism text, a tantric meditation guide, and as the material for comparative philosophy. Taken together, the translations and essays that form Elaborations on Emptiness demonstrate why commentary is as central to modern scholarship on Buddhism as it was for ancient Buddhists. Lopez reveals unexpected points of instability and contradiction in the Heart Sutra, which, in the end, turns out to be the most malleable of texts, where the logic of commentary serves as a tool of both tradition and transgression.