BENEATH man's thin veneer of consciousness lies a relatively uncharted realm of mental activity, the nature and function of which have been neither systematically explored nor adequately conceptualized. Despite numerous clinical and research reports on daydreaming, sleep and dream states, hypnosis, sensory deprivation, hysterical states of dissociation and depersonalization, pharmacologically induced mental aberrations, and so on, there has been little attempt made to organize this scattered information into a consistent theoretical system. It is my present intention to integrate and discuss current knowledge regarding various altered states of consciousness in an effort to determine (a) the conditions necessary for their emergence, (b) the factors which influence their outward manifestations, (c) their relatedness and/or common denominators, and (d) the adaptive or maladaptive functions which these states may serve for man.
For the purpose of discussion, I shall regard "altered state(s) of consciousness" [hereafter referred
LUDWIG AM. Altered States of Consciousness. Arch Gen Psychiatry. 1966;15(3):225–234. doi:10.1001/archpsyc.1966.01730150001001