The word ‘āstika,’ derived from the verb ‘asti’ (‘exists’) generally denotes anyone who believes in the existence of God and higher worlds like heaven, immortality of the soul, theory of karma and reincarnation and so on. Sometimes the word is used in the more restricted sense of one who believes in the authority of the Vedas. In this sense, the six well-known systems of Indian philosophy are called ‘āstika’ as opposed to the Cārvāka, the Jaina and the Bauddha systems, which are designated as ‘nāstika’ or ‘non-believing.’
When the king Parīkṣit, the grandson of the Pāṇḍava prince Arjuna died of snakebite, his son Janamejaya performed a sarpayāga or snake sacrifice in which hundreds of innocent snakes were being immolated. The final offering was to be Takṣaka, the king of snakes of the nether world, the chief ‘culprit’ who had bitten and killed Parīkṣit. Just then there appeared on the scene a young sage, Āstīka by name, the son of the Jaratkāru couple, and stopped the atrocious sacrifice. His mother was the sister of Vāsuki. He had been specially deputed to save the life of Vāsuki and all his subjects as also his followers, with his sweet speech and convincing logic. Āstīka was able to win over the king Janamejaya and extract the boon he wanted. Vāsuki and the snake species were thus saved from total annihilation.