Nobody can define an altered state without first defining normal
Psychologists still lack an agreed definition of an altered state of consciousness, because any attempt depends on pinning down what an ordinary waking mind is. Yet humans may have chased such states for 30,000 years, through dancing, plants and meditation, long before science dismissed and then rediscovered them.
The phrase was attached to hypnosis by 1892, though whether hypnosis truly counts is still argued. Max Mailhouse used it about epilepsy in a 1904 conference talk, a usage that survives. Arnold M. Ludwig offered the first formal definition in 1966: a mental state, brought on by bodily, psychological or chemical means, that departs enough from a person's usual alert experience to be noticed by them or an observer. Charles Tart popularised the term from 1969 and stressed that such states differ in quality, not just degree, from a baseline.
Later refinements kept the focus on inner experience. Farthing in 1992 added that the change is temporary or reversible and might go unrecognised at the time, and he listed fourteen dimensions of experience, several of which must shift together. A 2016 working definition by Schmidt suits laboratory work: compare a short episode, lasting minutes to hours, with a person's felt baseline, and measure the pattern of change across several factors with questionnaires, since an altered state is multidimensional rather than one dial turned up.
Science has swung between dismissal and fascination. Under behaviourism in the early 20th century these states were treated as signs of intoxication or even possession. William James revived interest by studying mystical and drug-induced experience, helping rehabilitate introspection. The upheavals of the 1960s widened acceptance, and researchers such as Abraham Maslow, Stanislav Grof and Walter Pahnke explored possible benefits; Pahnke's Good Friday Experiment suggested psilocybin could trigger mystical experiences. Harsher states, like dissociation after trauma, drew far less attention.
Classification schemes abound. Dieter Vaitl sorted states into five categories by how they arise, from fasting to hypnosis to near-death experience. Adolph Dittrich proposed three dimensions shared across methods, including oceanic boundlessness and dread of ego dissolution. Michael Winkelman placed meditation, hypnosis and psychedelics in an integrative mode alongside waking, deep sleep and dreaming. Ancient examples range from the rites of Dionysus to the Eleusinian Mysteries.
Source: Altered state of consciousness
