The time has gone by when any one man could hope to write an adequate text book of psychology. The science has now so many branches, so many methods, so many fields of application, and such an immense mass of data of observation is now on record, that no one man can hope to have the necessary familiarity with the whole. But, even when a galaxy of learning and talent shall have written the text book of the future, there will still be need for the book which will introduce the student to his science, which will aim at giving him at the outset of his studies a profitable line of approach, a fruitful way of thinking of psychological problems, and a terminology as little misleading as possible. The present volume is designed to render these services.