In spirituality, a medium or spirit medium (plural mediums) is an individual who claims to have the ability to receive messages from spirits (discorporate entities), or claims that he or she can channel such entities — that is, write or speak in the voice of these entities rather than in the medium's own voice.
While skeptics believe such individuals are either self-deluded or simply charlatans who engage in cold reading, popular mediums often have many followers who believe strongly in their purported abilities. In some cases mediums have produced personal information (allegedly told to them by a spirit) to their clients well above guessing rates.
Examples of popular modern-day (mental) mediums include Derek Acorah, Alison Dubois, Esther Hicks, Sylvia Browne, John Edward, Betty Shine, and James Van Praagh.
Harry Houdini was a famous magician who became a debunker of mediums later in life and, indeed, even in death, because he left a ten-word passphrase with his wife that a medium should say in order to prove they were channelling him. Although many people did claim to channel Houdini, no-one was able to reproduce the passphrase.
Mediumistic automatism
Mediumistic automatism is the automatism associated with a medium receiving supernatural messages from ghosts, spirits or the like, the expression of such messages (in speech, writing or drawings) lacking conscious control or intervention by the medium.