In fact, documented cases began long before, such as the book From India to the Planet Mars: A study of a case of somnambulism with glossolalia written in 1900 about an 1894 journey, contemporary with Freud's Interpretation of Dreams.
Multiples have had many faces throughout history, perhaps best known for demonic possession, changelings, and possession trances. And the language of multiplicity, and images of multiplicity, are commonly coloring our culture.
There are common features to multiplicity, common structures and a common cause for nearly all multiples: the adaptability of people when survival is threatened, whether the threat is real or imaginary. Not all multiplicity is traced to abuse, however, and this manual will seek to cover every plausible angle as long as there are contributions for it.
This section is an introduction to the basic features of multiplicity.