Charvaka
The school holds direct perception, empiricism, and conditional inference as proper sources of knowledge, embraces philosophical skepticism, and rejects ritualism and supernaturalism. It also rejects supernatural concepts like God, the soul, and metaphysical concepts like the Afterlife (reincarnation) and samsara. It used to be a popular belief system in ancient India, although Charvaka doctrine disappeared by the end of the medieval period. Its onetime importance is confirmed by the lengthy attempts to disprove it found in both Buddhist and Hindu philosophical texts, which also constitute the main sources for knowledge of the doctrine. Charvaka also rejects the caste system.