The poets may be better psychologists than the psychologists and philosophers; but they are men of feeling rather than of understanding, and at least one-sided in their consideration of the subject. They cannot see the deep shadow behind the light and sunny warmth of that from which they draw their inspiration. The poetry of all times and nations would furnish inexhaustible material for a monograph on the psychology of love; but the great problem can be solved only with the help of Science, and especially with the aid of Medicine, which studies the psychological subject at its anatomical and physiological source, and views it from all sides. Perhaps it will be possible for medical science to gain a stand-point of philosophical knowledge midway between the despairing views of philosophers like Schopenhauer and Hartmann[2] and the gay, _näive_ views of the poets. It is not the intention of the author to lay the foundation of a psychology of the sexual life, though without doubt psychopathology would furnish many important sources of knowledge to psychology. The purpose of this treatise is a description of the pathological manifestations of the sexual life and an attempt to refer them to their underlying conditions. The task is a difficult one, and, in spite of years of experience as alienist and medical jurist, I am well aware that what I can offer must be incomplete. The importance of the subject for the welfare of society, especially forensically, demands, however, that it should be examined scientifically. Only he who, as a medico-legal expert, has been in a position where he has been compelled to pass judgment upon his fellow-men, where life, freedom, and honor were at stake, and realized painfully the incompleteness of our knowledge concerning the pathology of the sexual life, can fully understand the significance of an attempt to gain definite views concerning it. Even at the present time, in the domain of sexual criminality, the most erroneous opinions are expressed and the most unjust sentences pronounced, influencing laws and public opinion. He who makes the psychopathology of sexual life the object of scientific study sees himself placed on a dark side of human life and misery, in the shadows of which the godlike creations of the poet become hideous masks, and morals and æsthetics seem out of place in the “image of God.” It is the sad province of Medicine, and especially of Psychiatry, to constantly regard the reverse side of life,—human weakness and misery. Perhaps in this difficult calling some consolation may be gained, and extended to the moralist, if it be possible to refer to morbid conditions much that offends ethical and æsthetic feeling. Thus Medicine undertakes to save the honor of mankind before the Court of Morality, and individuals from judges and their fellow-men. The duty and right of medical science in these studies belong to it by reason of the high aim of all human inquiry after truth.