Rudely classifying the principal fields of human difficulty, we find one large proportion lies in the sex-relation, and another in the economic relation, between the individual constituents of society. To speak broadly, the troubles of life as we find them are mainly traceable to the heart or the purse. The other horror of our lives—disease—comes back often to these causes,—to something wrong either in economic relation or in sex-relation. To be ill-fed or ill-bred, or both, is largely what makes us the sickly race we are. In this wrong breeding, this maladjustment of the sex-relation in humanity, what are the principal features? We see in social evolution two main lines of action in this department of life. One is a gradual orderly development of monogamous marriage, as the form of sex-union best calculated to advance the interests of the individual and of society. It should be clearly understood that this is a natural development, inevitable in the course of social progress; not an artificial condition, enforced by laws of our making. Monogamy is found among birds and mammals: it is just as natural a condition as polygamy or promiscuity or any other form of sex-union; and its permanence and integrity are introduced and increased by the needs of the young and the advantage to the race, just as any other form of reproduction was introduced. Our moral concepts rest primarily on facts. The moral quality of monogamous marriage depends on its true advantage to the individual and to society. If it were not the best form of marriage for our racial good, it would not be right. All the way up, from the promiscuous horde of savages, with their miscellaneous matings, to the lifelong devotion of romantic love, social life has been evolving a type of sex-union best suited to develope and improve the individual and the race. This is an orderly process, and a pleasant one, involving only such comparative pain and difficulty as always attend the assumption of new processes and the extinction of the old; but accompanied by far more joy than pain. But with the natural process of social advancement has gone an unnatural process,—an erratic and morbid action, making the sex-relation of humanity a frightful source of evil. So prominent have been these morbid actions and evil results that hasty thinkers of all ages have assumed that the whole thing was wrong, and that celibacy was the highest virtue. Without the power of complete analysis, without knowledge of the sociological data essential to such analysis, we have sweepingly condemned as a whole what we could easily see was so allied with pain and loss. But, like all natural phenomena, the phenomena of sex may be studied, both the normal and the abnormal, the physiological and the pathological; and we are quite capable of understanding why we are in such evil case, and how we may attain more healthful conditions.