Nyaya is one of the six orthodox schools of Indian philosophy. It is known for its systematic epistemology and logic. Pramanas (means of valid knowledge) are central to Nyaya, and these are typically identified as perception (pratyaksha), inference (anumana), comparison (upamana), and testimony (shabda). The terms 'cognition' and 'apprehension' can be seen as encompassing the outcomes or processes related to these pramanas.