What are the six schools of Hindu philosophy?

Hindu philosophy has six orthodox schools, called darshanas, a word meaning "viewpoint or perspective", from a root meaning "to see, to experience". They are the astika schools, defined by their acceptance of the Vedas as an authoritative source of knowledge: Samkhya, Yoga, Nyaya, Vaisheshika, Mimamsa and Vedanta.

Samkhya is the oldest of the orthodox systems, with origins in the 1st millennium BCE. It espouses a dualism between witness-consciousness (purusha) and "nature" (prakriti), and it aims at realising purusha as distinct from prakriti, which is held to end transmigration and lead to absolute freedom. Yoga accepts Samkhya's psychology and metaphysics but is considered theistic, because it accepts a personal god.

Nyaya is the school of logic and of how to know things; its most significant contributions were its systematic development of logic, methodology and epistemology. Vaisheshika is a naturalist school and a form of atomism: all objects in the physical universe are reducible to atoms.

Mimamsa is about ritual. It held that dharma meant rituals and duties, not gods, because gods existed only in name. Vedanta contains various traditions that mostly embrace nondualism.

These are not the only Indian philosophies. Buddhism, Jainism, Charvaka and Ajivika are called nastika, or heterodox, philosophies. Today, of the six, Vedanta and Yoga are the most prominent.