An illuminating gateway to Indian philosophy and its explication in Tibet. Among the many works produced in the rich philosophical tradition of India’s classical age, few have had more impact than Dharmakirti’s Commentary on Valid Cognition (Pramanavarttika). Composed in India in the seventh century, it became the cornerstone for the study of logic and epistemology in the Tibetan Buddhist tradition. An important addition to any collection for the Sakya practitioner, Light of Samantabhadra translates the work of one of the premier scholars of the Sakya school, Gorampa Sonam Sengé (1429–89). Gorampa here illuminates the first two chapters of Dharmakirti’s treatise, those on using inference to enlighten oneself (svarthanumana) and on establishing valid cognition (pramanasiddhi), both to determine the authority of the Buddha as a valid teacher and to eliminate the cognitive obstacles to awakening. The root text is composed in compact verses, and these are translated here along with Gorampa’s word-by-word commentary that reveals their often-veiled meanings. These chapters explore key issues in the philosophy of language and the nature of conventional designation, the way to employ sound reasoning, the proof of past and future lives, and the way to eliminate the view of self. In the skilled hands of translator Gavin Kilty, these insights are made accessible to contemporary readers.