Original scriptures of the Ājīvika school of philosophy may once have existed, but these are currently unavailable and probably lost. Their theories are extracted from mentions of Ajivikas in the secondary sources of ancient Hindu Indian literature, particularly those of Jainism and Buddhism which polemically criticized the Ajivikas. The Ājīvika school is known for its "Niyati" doctrine of absolute determinism (fate), the premise that there is no free will, that everything that has happened, is happening and will happen is entirely preordained and a function of cosmic principles. Ājīvika considered the karma doctrine as a fallacy. Ājīvikas were atheists and rejected the authority of the Vedas, but they believed that in every living being is an "ātman" – a central premise of Hinduism and Jainism.