Four ways to know: perception, inference, comparison, and testimony. He built Indian logic from the ground up.
Akshapada Gautama founded the Nyaya school, one of the six orthodox systems of Indian philosophy. His Nyaya Sutras lay out a complete theory of knowledge, argumentation, and debate. He identified four valid means of knowledge: direct perception, logical inference, comparison with known objects, and reliable testimony. He also formalized the five-part syllogism used in Indian philosophical debate. The Nyaya system became the standard framework for logical argument across all Indian philosophical traditions, including those that disagreed with its metaphysics.
“Perception, inference, comparison, and testimony are the four valid means of knowledge.”
Akshapada Gautama established Nyaya, the school of logic and epistemology, as one of the six classical systems of Indian philosophy. Where other schools asked what is real, Nyaya asked: how do you know?
Composed the foundational text of Indian logic, laying out four valid means of knowledge: perception, inference, comparison, and testimony. The Nyaya Sutras also developed a five-part syllogism that became the standard form of argument across Indian philosophical traditions.