While a short work of only eight verses and a three-page autocommentary, the Investigation of the Percept has inspired epistemologists for centuries and has had a wide-ranging impact in India, Tibet, and China. Dignaga, one of the major figures in Buddhist epistemology, explores issues such as the relation between the mind and its percepts, the problems of idealism and realism, and the nature of intentionality in this brief but profound text. This volume provides a comprehensive history of the text in India and Tibet from 5th century India to the present day. This team of philologists, historians of religion and philosophers who specialize in Tibetan, Sanskrit and Chinese philosophical literature has produced the first study of the text and its entire commentarial tradition. Their approach makes it possible 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 Dignāga's thought and demonstrate the diversity of commentarial approaches to his text. The comprehensive nature of the work reveals the richness of commentary in Indian and Tibetan Buddhism and shows surprising parallels between the modern West and traditional Buddhist philosophy.