INTRODUCTION.

I AM glad to contribute to this book of Dr. Boris Sidis a few words of introduction, which may possibly gain for it a prompter recognition by the world of readers who are interested in the things of which it treats. Much of the experimental part of the work, although planned entirely by Dr. Sidis, was done in the Harvard Psychological Laboratory, and I have been more or less in his confidence while his theoretic conclusions, based on his later work in the Pathological Institute of the New York State Hospitals, were taking shape.

The meaning of personality, with its limits and its laws, forms a problem which until quite recently had to be discussed almost exclusively by logical and meta-physical methods. Within the past dozen years; how-ever, an immense amount of new empirical material had been injected into the question by the observations which the "recognition" by science of the hypnotic state set in motion. Many of these observations are pathological : fixed ideas, hysteric attacks, insane delusions, mediumistic phenomena, etc. And altogether, although they are far from having solved the problem of personality, they must be admitted to have trans-formed its outward shape. What are the limits of the consciousness of a human being ? Is " self" conscious-

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