My opinions on the sexual question are based, on the one hand, on my scientific study of the human brain, and on the other hand on the long personal experience of an alienist who has devoted himself almost as much to normal mentality and questions of social hygiene as to pathological mentality. I have, however, been obliged to rely on the fundamental work of Westermark with regard to ethnology, this subject being strange to me. Concerning sexual psycho-pathology I have followed the classification of Krafft-Ebing.

The sexual question is extraordinarily complex, and we cannot expect to find a simple solution for it as we can for the questions of alcoholism, slavery, torture, etc. The latter are solved in one word—suppression. Suppression of slavery and torture; suppression of the usage of alcoholic drinks. We are concerned here with ulcers artificially produced and preserved in human society; ulcers which must be simply extirpated. Their suppression is nothing but beneficial, since, far from being connected with the normal conditions of human existence, they place it in peril. Sexual instinct and sentiment, on the contrary, have their roots in life itself; they are intimately bound up with humanity, and therefore require quite a different treatment. But human society has guided them into false and pernicious ways. It is important to turn them from these in order to tranquilize and regulate their course by damming them up and canalizing them.

The fundamental axiom of the sexual question is as follows:

With man, as with all living beings, the constant object of all sexual function, and consequently of sexual love, is the reproduction of the species. It is therefore necessary to treat the question from the point of view of the natural sciences, physiology, psychology and sociology. This has already been done more than once, but usually in erudite treatises which only look upon one side of the question; or, on the other hand, in a superficial and often frivolous manner.

To ensure happiness, humanity should desire to reproduce itself in a manner which elevates progressively all the physical and mental faculties of man, with regard to health and bodily strength, as much as to sentiment, intelligence, will, creative imagination, love of work, joy of living, and the sentiment of social solidarity. Every attempt made to solve the sexual question should, therefore, be directed toward the future and toward the happiness of our descendants.

It requires much disinterestedness to attempt seriously any sexual reform. But, as the human subject is by nature extremely weak, as his views are limited, especially in the matter which concerns us, it is absolutely necessary, if we would avoid Utopia, to adapt the fundamental aim of sexual union to happiness and joy, even to the natural weakness of man.

The fundamental difficulty of the problem lies in the necessity for such an adaptation, and this difficulty requires us to make a clean sweep of prejudices, traditions and prudery. It is this which we wish to attempt.

Considered from an exalted point of view, sexual life is beautiful as well as good. What there is in it which is shameful and infamous is the obscenity and ignominy caused by the coarse passions of egoism and folly, allied with ignorance, erotic curiosity and mystic superstition, often combined with social narcotic intoxication and cerebral anomalies.

We shall divide our subject into nineteen chapters. Chapters I to VII deal with the natural history and psychology of sexual life; Chapter VIII with its pathology, and Chapters IX to XVIII with its social role, that is to say, its connection with the different domains of human social life.