Indian philosophy refers to ancient philosophical traditions which encompasses the systems of thought and reflection that developed on the Indian subcontinent. The principal schools are classified as either

Orthodox or āstika(astika, from the Sanskrit asti "there is") : They rely on the authority of the Vedas

Heterodox or nāstika: Systems of thought reject the authority of the Vedas and the superiority of Brahmins in matters of philosophical reflection.

There are six major schools of orthodox

• Nyāya ("Rule" or "Method"),
• Vaiśeṣika ("Particular"),
• Saṃkhya ("Enumeration" or "Number"),
• Yoga ("Union"),
• Purva Mīmāṃsā (or Mīmāṃsā, "Reflection" or "Critical Investigation")
• Vedanta ("conclusion of the Veda").

In contrast there are four major schools of heterodox

• Buddhism,
• Jainas ("Followers of Conquerors" from the Sanskrit verb ji "to conquer"),
• Ājīvikas,
• Physicalist Cārvākas