Mediumship became quite popular in the 19th-century United States and the United Kingdom after the rise of Spiritualism as a religious movement. Modern Spiritualism is said to date from practices and lectures of the Fox sisters in New York State in 1848. The trance mediums Paschal Beverly Randolph and Emma Hardinge Britten were among the most celebrated lecturers and authors on the subject in the mid-19th century. Allan Kardec coined the term Spiritism around 1860.[12] Kardec claimed that conversations with spirits by selected mediums were the basis of his The Spirits' Book and later, his five-book collection, Spiritist Codification.

Senses used by mental mediums are sometimes defined differently from in other paranormal fields. A medium is said to have psychic abilities but not all psychics function as mediums. The term clairvoyance, for instance, may include seeing spirit and visions instilled by the spirit world. The Parapsychological Association defines "clairvoyance" as information derived directly from an external physical source.[37]