An altered state of consciousness (ASC), also called altered state of mind or mind alteration, is any condition which is significantly different from a normal waking state. By 1892, the expression was in use in relation to hypnosis, though there is an ongoing debate as to whether hypnosis is to be identified as an ASC according to its modern definition. The next retrievable instance, by Dr Max Mailhouse from his 1904 presentation to conference, however, is unequivocally identified as such, as it was in relation to epilepsy, and is still used today. In academia, the expression was used as early as 1966 by Arnold M. Ludwig and brought into common usage from 1969 by Charles Tart. It describes induced changes in one's mental state, almost always temporary. A synonymous phrase is "altered state of awareness". Definitions There is no general definition of an altered state of consciousness, as any definitional attempt would first have to rely on a definition of a normal state of consciousness. Attempts to define the term can however be found in philosophy, psychology and neuroscience. There is no final consensus on what the most accurate definition is. In the following, the best established and latest definitions are provided: Arnold M. Ludwig attempted a first definition in 1966. "An altered state is any mental state(s), induced by various physiological, psychological, or pharmacological maneuvers or agents, which can be recognized subjectively by the individual himself (or by an objective observer of the individual) as representing a sufficient deviation in subjective experience of psychological functioning from certain general norms for that individual during alert, waking consciousness." Starting from this, Charles Tart focuses his definition on the subjective experience of a state of consciousness and its deviation from a normal waking state. "Altered states of consciousness are alternate patterns or configurations of experience, which differ qualitatively from a baseline state." Farthing's definition of an altered state of consciousness (ASC) is based on Charles Tart's terminology. Charles Tart described an altered state of consciousness as a profound change in the "overall pattern of subjective experiences". In order to define an ASC, Tart focuses on the importance of subjective experience. Farthing adds to his definition that an ASC is short-termed or at least reversible and that it might not even be recognized as an ASC at that moment. His definition relies only on subjective experience, leaving aside behavioral changes and physiological response.