In Hinduism, astika, literally means, one who believes in something. The term refers to the schools of philosophy that accept the authority of the Vedas. Hindus classify the systems of philosophy and religion into two categories – astika (orthodox) and nastika (heterodox). Astika schools or Astika Darsana believe in the authority of the Vedas, whereas nastika schools do not.
The important astika schools are – Samkhya, Yoga, Nyaya,
Vaiseshika, Mimamsa and Vedanta. In addition to these six astika systems, seven
more have been listed in the Sarvadarshanasamgraha of Madhavacharya. They are –
the philosophy of qualified non-dualism (of Ramanuja), the philosophy of dualism
(of Madhavacharya), the Pashpupata system of Nakulisha, the Shaiva philosophy,
the Pratyabhijna system or Kashmir Shaivism, the Raseshvara philosophy and the grammatical
philosophy of Panini. Moreover, all the other Shaiva, Shakta, Vaishnava and
Tantra schools of philosophy come under the astika fold.
The term astika comes from the words asti (it is). The reference
to the concept of existence involved in this term is primarily towards some
higher and subtle intelligent order of the universe. The acceptance of any form
of such subtle and intelligent universal order logically implies the
possibility of the universal validity of apta jnana (revealed knowledge). As
such, the directly- perceived knowledge of persons having intuitive insight may
be rightly taken as trustworthy and authoritative.
Vedic literature is a compilation of various instances of
such intuitively revealed knowledge, coming from different ancient Vedic rishis
(sages). That is why the Vedic rishis are not treated as authors of Vedic
passages; rather it is believed that they intuitively grasped those knowledge-pieces,
in the form of fixed sequences of vibrations. Thus, despite superficial differences
among various Vedic passages, the astika systems believe in t necessity of a
deeper harmony among them, since they are all revelations of the same truth and
reality. This fundamental belief of the astika systems gave rise to various
commentaries on Vedic literature with the purpose of ex-pounding the common
ground of all the passages, viz., the universal Reality.