It suggests almost inconceivable possibilities as to our own nature, and leaves us appalled on the brink of a new world of being of which until recently most of us were unaware.
There are no papers of such absorbing interest in the whole of the "Proceedings of the Society for Psychical Research" as those which deal with the question of the Personality of Man.

"I," what am I?
What is our Ego?
Is this Conscious Personality which receives impressions through the five senses, and through them alone, is it the only dweller in this mortal tabernacle?
May there not be other personalities, or at least one other that is not conscious, when we are awake, and alert, and about, but which comes into semi-consciousness when we sleep, and can be developed into complete consciousness when the other personality is thrown into a state of hypnotic trance?
In other words, am I one personality or two?
Is my nature dual?
As I have two hemispheres in my brain, have I two minds or two souls?
The question will, no doubt, appear fantastic in its absurdity to those who hear it asked for the first time; but those who are at all familiar with the mysterious but undisputed phenomena of hypnotism will realize how naturally this question arises, and how difficult it is to answer it otherwise than in the affirmative.

Every one knows Mr.Louis Stevenson's wonderful story of "Dr.Jekyll and Mr.Hyde." The dual nature of man, the warfare between this body of sin and death, and the spiritual aspirations of the soul, forms part of the common stock of our orthodox belief.

But the facts which recent researches have brought to light seem to point not to the old theological doctrine of the conflict between good and evil in one soul, but to the existence in each of us of at least two distinct selfs, two personalities, standing to each other somewhat in the relation of man and wife, according to the old ideal when the man is everything and the woman is almost entirely suppressed.
Every one is familiar with the phenomenon of occasional loss of memory.
Men are constantly losing consciousness, from disease, violence, or violent emotion, and emerging again into active life with a gap in their memory.

Nay, every night we become unconscious in sleep, and rarely, if ever, remember anything that we think of during slumber.