I do not expect this book to stand upon its literary merits; for if it is unsound in principle, felicity of diction cannot save it, and if sound, homeliness of expression cannot destroy it. My primary object in offering it to the public is to assist in bringing Psychology within the domain of the exact sciences. That this has never been accomplished is owing to the fact that no successful attempt has been made to formulate a working hypothesis sufficiently comprehensive to embrace all psychic phenomena. It has, however, long been felt by the ablest thinkers of our time that all psychic...