The principle of divorce forms the most important foundation at once for a future reformation of marriage, and for a rational view, one doing equal justice to the interests of society and those of the individual, of the relations between man and wife. By the introduction of divorce, the State itself has recognized the purely personal character of conjugal relations, and has admitted that circumstances arise in which the marriage ceases to fulfil its aims and becomes injurious to both parties. =Thus the State has proclaimed the rights of the individual personality in the married state.= In the marriage problem, the so-called “=duplex sexual morality=” also plays an important part--that is to say, the idea that man is by nature inclined to polygamy, but woman to monogamy. Herein, indeed, the thoroughly correct idea was dominant that the cohabitation of one woman with several men--be it understood we refer to simultaneous cohabitation--is harmful to the offspring. From this, however, the only permissible inference is that for the purposes of the procreation of children and of racial hygiene “monogamy” can be demanded of woman on rationalistic grounds--that is to say, the intercourse of woman should be restricted to a single man during such a time and for such a purpose. But it is not legitimate from these considerations to deduce the necessity of permanent “monandry” for woman. I will consider this question somewhat more exactly, and in doing so will refer to the interesting essay of Rudolph Eberstadt on “The Economic Importance of Sanitary Conditions” in relation to marriage, being the concluding chapter of “Health and Disease in Relation to Marriage and the Married State,” by Senator and Kaminer (Rebman, 1906), because here we find a very clear recognition of the confusion between monogamy and monandry. According to Eberstadt, there are above all two things characteristic of modern civilized marriage--in the first place, the higher rank allotted to the husband in the married state, and, in the second place, the increased demand for prenuptial purity and for conjugal fidelity on the part of the wife. The husband demands from his wife, in addition to his own mastership in the married state, also sexual continence before marriage and unconditional fidelity during marriage. But the husband does not recognize that corresponding duties are imposed on himself.