Illusions : A Psychological Study

The present volume takes a wide survey of the field of error embracing in its view not only the illusions of sense dealt with in treatises on physiological optics etc. but also other errors familiarly known as illusions and resembling the former in their structure and mode of origin. I have throughout endeavoured to keep to a strictly scientific treatment that is to say the description and classification of acknowledged errors and the explanation of these by a reference to their psychical and physical conditions. (From Preface)