Psychonautics (from the Ancient Greek ψυχή psychē 'soul, spirit, mind' and ναύτης naútēs 'sailor, navigator') refers both to a methodology for describing and explaining the subjective effects of altered states of consciousness, especially an important subgroup called holotropic states, including those induced by meditation or mind-altering substances, and to a research cabal in which the researcher voluntarily immerses themselves into an altered mental state in order to explore the accompanying experiences.
The term has been applied diversely, to cover all activities by which altered states are induced and utilized for spiritual purposes or the exploration of the human condition, including shamanism, lamas of the Tibetan Buddhist tradition, sensory deprivation, and archaic/modern drug users who use entheogenic substances in order to gain deeper insights and spiritual experiences. A person who uses altered states for such exploration is known as a psychonaut.
The term psychonautics derives from the prior term psychonaut, usually attributed to German author Ernst Jünger who used the term in describing Arthur Heffter in his 1970 essay on his own extensive drug experiences Annäherungen: Drogen und Rausch (literally: "Approaches: Drugs and Inebriation"). In this essay, Jünger draws many parallels between drug experience and physical exploration—for example, the danger of encountering hidden "reefs."