First published in 1931, the underlying assumption of is that of a psychological evolution in which mind is regarded not merely as developing in association with nervous and cerebral development, but as being itself the most important factor in the process. It is this assumption which gives meaning to the title that has been chosen for the book. It brings themes like is psychology a science; impulse and growth; the rise of consciousness; the three main lines of instinct; the variability of habit; development of intelligence; thought as judgment and reflection; the critical faculty; simple and complex emotions; ideals and idealization; voluntary activity; sex and conflict; and buried complexes and dreams. This is an interesting historical document for the students of psychology.