Traditionally ancient Hindu philosophy is divided into six āstika (Sanskrit: आस्तिक "orthodox") schools of thought, or darśanas (दर्शनस्, "views"), which accept the Vedas as supreme revealed scriptures. Three other nāstika (नास्तिक "heterodox") schools do not accept the Vedas as authoritative. The āstika schools are:

The nāstika schools are:

However, medieval philosophers like Vidyāraṇya classify Indian philosophy into sixteen schools, where schools belonging to Saiva, Pāṇini and Raseśvara thought are included with others, and the three Vedantic schools Advaita, Vishishtadvaita and Dvaita (which had emerged as distinct schools by then) are classified separately.

In Hindu history, the distinction of the six orthodox schools was current in the Gupta period "golden age" of Hinduism. With the disappearance of Vaisheshika and Mimamsa, it was obsolete by the later Middle Ages, when the various sub-schools of Vedanta (Dvaita "dualism", Advaita Vedanta "non-dualism" and others) began to rise to prominence as the main divisions of religious philosophy. Nyaya survived into the 17th century as Navya Nyaya "Neo-Nyaya", while Samkhya gradually lost its status as an independent school, its tenets absorbed into Yoga and Vedanta.