The Nyayavatara, erroneously ascribed by tradition to Siddhasena Divakara, was either the first or one of the first serious Jaina treatises on epistemology. Its author enters polemics with other – mostly Buddhist – epistemological schools and endeavours to establish a Jaina epistemological tradition of its own. Despite its importance, the work is rather secondary in the sense that it relies, for the most part, on the Buddhist logical legacy. The first extant commentary is the Nyayavatara-vivrti of Siddharsigani. Its significance is often underestimated, for its author was responsible for the subsequent development of Jaina epistemological thought to a much larger degree than it has so far been recognised. He refers to major philosophical schools of his times, e.g. to Sautrantika, Yogacara, Sunya-vada, Samkhya, Mimamsa, Nyaya, Vaisesika, Advaita-vedanta, the materialists, etc. The gloss (Tippana) of Devabhadra is in addition a useful source of quotations.