Dignāga (a.k.a. Diṅnāga, c. 480 – c. 540 CE) was an Indian Buddhist scholar and one of the Buddhist founders of Indian logic (hetu vidyā). Dignāga's work laid the groundwork for the development of deductive logic in India and created the first system of Buddhist logic and epistemology (Pramana). According to Georges B. Dreyfus, his philosophical school brought about an Indian "epistemological turn" and became the "standard formulation of Buddhist logic and epistemology in India and Tibet." Dignāga's thought influenced later Buddhist philosophers like Dharmakirti and also Hindu thinkers of the Nyaya school. Dignāga's epistemology accepted only "perception" (pratyaksa) and "inference" (anumāṇa) as valid instruments of knowledge and introduced the widely influential theory of "exclusion" (apoha) to explain linguistic meaning. His work on language, inferential reasoning and perception were also widely influential among later Indian philosophers. According to Richard P. Hayes "some familiarity with Dinnaga's arguments and conclusions is indispensable for anyone who wishes to understand the historical development of Indian thought." Dignāga was born in Simhavakta near Kanchipuram and very little is known of his early years, except that he took Nagadatta of the Pudgalavada school as his spiritual preceptor, before being expelled and becoming a student of Vasubandhu. Philosophy Dignāga mature philosophy is expounded in his magnum opus, the Pramāṇa-samuccaya. In chapter one, Dignāga explains his epistemology which holds that there are only two 'instruments of knowledge' or 'valid cognitions' (pramāṇa); "perception" or "sensation" (pratyakṣa) and "inference" or "reasoning" (anumāṇa). In chapter one, Dignāga writes: Sensation and reasoning are the only two means of acquiring knowledge, because two attributes are knowable; there is no knowable object other than the peculiar and the general attribute. I shall show that sensation has the peculiar attribute as its subject matter, while reasoning has the general attribute as its subject matter. Perception is a non-conceptual knowing of particulars which is bound by causality, while inference is reasonable, linguistic and conceptual. This conservative epistemic theory was in contrast to the Nyaya school who accepted other means of knowledge such as upamāṇa (comparison and analogy). Pratyakṣa Pratyakṣa is a kind of awareness that acquires information about particulars, and is immediately present to one of the senses. This is the topic of the first chapter of the Pramāṇa-samuccaya. For Dignāga, perception is pre-verbal, pre-conceptual and unstructured sense data. In chapter two of the Pramāṇa-samuccaya he writes: Sensation is devoid of structure. That cognition in which