Investigation of the Percept is a short (eight verses and a three page autocommentary) work that focuses on issues of perception and epistemology. Its author, Dignaga, was one of the most influential figures in the Indian Buddhist epistemological tradition, and his ideas had a profound and wide-ranging impact in India, Tibet, and China. The work inspired more than twenty commentaries throughout East Asia and three in Tibet, the most recent in 2014. This book is the first of its kind in Buddhist studies: a comprehensive history of a text and its commentarial tradition. The volume editors translate the root text and commentary, along with Indian and Tibetan commentaries, providing detailed analyses of the commentarial innovations of each author, as well as critically edited versions of all texts and extant Sanskrit fragments of passages. The team-based approach made it possible to study and translate a corpus of treatises in Sanskrit, Tibetan, and Chinese and to employ the methods of critical philology and cross-cultural philosophy to provide readers with a rich collection of studies and translations, along with detailed philosophical analyses that open up the intriguing implications of Dignaga's thought and demonstrate the diversity of commentarial approaches to his text. This rich text has inspired some of the greatest minds in India and Tibet. It explores some of the key issues of Buddhist epistemology: the relationship between minds and their percepts, the problems of idealism and realism, and error and misperception.