The last two hundred years have revolutionized nearly all of our deepest conceptions concerning the relations of human beings to religion, government, property, and to each other. New knowledge has given us partial control over vast forces of nature; and has so increased our mobility as almost to free us from limitations of space. We have had wonderful visions of the possibilities that lie in intelligent human cooperation, and have begun to realize them in a hundred new forms. In the midst of these compelling changes, women could no more remain undisturbed, within the confines of kitchen and nursery, than men could remain on their little New England farms or cobbling shoes and making tin pans in the petty workshops of a century ago. But meantime the special interests of women have been sadly confused because of the larger changes in which all human relations have been involved in this time of readjustment. Instead of talking of unquiet women to-day, we should talk of an unquiet world. In the midst of this confusion, most of those who have sought to secure a truer relation of women to the life around them have worked on the lines of minimizing sex differences. It has been felt that the educational, industrial, social and political limitations under which women rested were due to the desire of men to exploit them. Men, being free, had developed for themselves an ideal world of thought and work; and if women wished to be free and happy, they needed only to break down the barriers separating them from this man's world. Most of these barriers are now down; but the women who study in universities, teach in the schools, maintain offices as doctors or lawyers, collect news for the press, tend spindles in a factory or sell ribbons at a counter have found that the man's world is far from ideal and that by entering it they have not escaped the special limitations of their sex. Everywhere the feeling is abroad that, instead of having arrived at a destination, women have embarked on a journey fraught with many uncertainties. This volume has been written in the belief that men and women alike will achieve greatest freedom and happiness, not by minimizing sex differences, but by frankly recognizing them and using them. If we could reduce men and women to sameness, we should destroy at least half the values of human life. They are not alike; but they are perfectly supplementary. The unit can never be a man nor a woman; it must always be a man and a woman. This means that in all the activities essential to human development men and women must carefully study to find what each can best provide.