To many it is surprising to find that the word "sex" has never been used in such degraded connections as has the word "love," and that it has not been half so much misunderstood. There is no obvious vulgarity in the lexicographer's definitions of the word "sex." It simply means, as the science of biology points out so clearly, that the perpetuation of human life, and of most other species of life, has been intrusted to pairs of individuals which are of the two kinds commonly called the sexes, male and female. Why nature determined that each new life in the vast majority of species should develop from two other lives has long been a biological puzzle, and most satisfactory of the answers given is that bi-parental origin of new individuals allows for new combinations of heritable qualities from two lines of descent. However, such a biological explanation of the relation of the two sexes to double parentage is of relatively little practical significance in present-day human life when compared with the fact that out of the necessity for life's perpetuation by two cooperating individuals there has grown psychical or spiritual love with all its splendid possibilities that are evident in ideal family life. Moreover, the influence of sex in human life has extended far beyond the family (that is, that group of individuals who stand related to one another as husband, wife, parents, and children), for it is a careless observer indeed who does not note in our daily life many social and psychical relationships of men and women who have no mutual interests relating to the biological processes of race perpetuation. Of course, the psychologist recognizes that far back of the platonic contact of the sexes on social and intellectual lines is the suppressed and primal instinct that provides physical unions for race perpetuation. However, this is of no practical interest, for, as a matter of fact, the primal instincts are quite subconscious in the usual social relations between the sexes. [Sidenote: The larger view of sex.] There is grandeur in this view of sex as originally a provision for perpetuation of life by two cooperating individuals, later becoming the basis of conjugal affection of the two individuals for each other and of their parental affection for their offspring, and finally leading to social and intellectual comradeship of men and women meeting on terms which are practically free from the original and biological meaning of sex. Instead, then, of trying to keep sex, both word and fact, in the background of the new educational movement, I believe it is best to work definitely for a better understanding of the part which sex plays in human life, as outlined in the preceding paragraph. Hence, in these lectures I shall never go aside in order to avoid either the word or the idea of sex; on the contrary, I shall attempt to direct the discussion so as to emphasize the larger and very modern view of the relationship of sex and human life.