ABSTRACT
THE problem of the splitting of consciousness which occupies such a prominent place in the study of hysteria assumes still greater importance when we come to consider those forms of disintegration which are commonly described under the name of double or multiple personality. The essential feature of this condition is the occurrence in one individual of two or more phases of conscious life, each of which shows the characteristics of personality, yet differs so much from the other in important respects that it seems to be the manifestation of a different personality. Such a description of what constitutes double personality emphasizes the fact that here as elsewhere in nature we can draw no hard-and-fast line between the normal and the abnormal, or between the usual and the unusual. The lapses of memory which are common in everyday life, the changes of mood which accompany changes in the body and its functional activity, the aberrations of conduct to which most men are liable in some degree, are the same in kind as those that are met with in more pronounced form in multiple personality. Continuity of memory is one of the most essential factors in producing the feeling of personal identity which each of us has from day to day, and any gap in the memory chain will tend to produce some alteration, however slight, in the structure of personality. If we cannot remember the events of yesterday, we are not quite the same persons as we should have been if we could remember them, and our conduct will be different in some respects from what it would have been if no loss of memory had occurred. So, if we forget the events of a week, a month, or a year, our personalities will appear constricted to the extent of the forgotten experiences—in so far, at least, as personality is revealed by what enters into consciousness.
