  Theory of knowledge, pramāṇa-śāstra, is a rich genre of Sanskrit literature, spanning almost twenty centuries, carried out in texts belonging to distinct schools of philosophy. Debate across school occurs especially on epistemological issues, but no author writes on knowledge independently of the sort of metaphysical commitment that defines the various classical systems (darśana), realist and idealist, dualist and monist, theist and atheist, and so on. And every one of the dozen or so major schools from early in its history takes a position on knowledge and justification, if only, as with the Buddhist skeptic (Prasaṅgika), to attack the theories of others.  There are nevertheless many common epistemological assumptions or attitudes, the most striking of which is a focus on a belief’s source in questions of justification. Mainstream classical Indian epistemology is dominated by theories about pedigree, i.e., views about knowledge-generating processes, called pramāṇa, “knowledge sources.” The principal candidates are perception, inference, and testimony. Other processes seem not truth-conducive or reducible to one or more of the widely accepted sources such as perception and inference. However, surprising candidates such as non-perception (for knowledge of absences) and presumption (defended as distinct from inference) provoke complex arguments especially in the later texts—from about 1000 when the number of Sanskrit philosophical works of some of the schools begins to proliferate almost exponentially. The later texts present more intricate views and arguments than the earlier from which the later authors learned. Classical Indian philosophy is an unbroken tradition of reflection expressed in the pan-Subcontinent intellectual language of Sanskrit. Or, we should say it is comprised of interlocking traditions since there are the distinct schools, all nevertheless using Sanskrit and engaging with other schools. Later authors expand and carry forward positions and arguments of their predecessors.