Āstika literally means "there is, there exists" and nāstika means "not āstika". These have been concepts used to classify Indian philosophies by modern scholars, and some Hindu, Buddhist and Jaina texts. Āstika 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 ātman, or as those who accept the existence of Ishvara. In contrast, nāstika are those who deny the respective definitions of āstika.