Psychonautics (from the Greek ψυχή psychē ["soul", "spirit" or "mind"] and ναύτης na\xfatēs ["sailor" or "navigator"] — "a sailor of the soul" refers both to a methodology for describing and explaining the subjective effects of altered states of consciousness, including those induced by meditation or mind-altering substances, and to a research paradigm in which the researcher voluntarily immerses himself or herself 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.