Astika ("there is, there exists") and
nastika ("not astika") are concepts used by the Brahmanical tradition, and modern scholars to classify and contrast Indian philosophies.
Astika has been defined in one of three ways; as those who accept the
epistemic authority of the
Vedas, as those who accept the existence of
atman, or as those who accept the existence of
Ishvara. In contrast,
nastika are those who deny the respective foundational definitions of
astika.