Originally published in 1920. PREFACE: That period of life technically known as Adolescence, untechnically as the time of youth, and colloquially as the Teen age, covering the years from the advent of puberty to the attainment of maturity, and roughly identical with the days of high school and college education, has been widely and carefully studied, from every point of view, during recent years, and our knowledge of it has been correspondingly enriched. The purpose of the present work is not primarily to add to the number of those valuable records which embody the results of investigations into the adolescent mind from this or that point of view; but rather to survey the whole field, having in mind the leading facts, as presented in these psychological and biological researches, as well as the fundamental categories of valuation, as set forth in the philosophy of morals, of religion, and of education....Many of the earliest books, particularly those dating back to the 1900's and befor