Nature has endowed man as well as the other animals with peculiar instincts, destined to preside over the different functions and to ensure their accomplishment. And, at the same time, it has enabled him in a measure to deceive those instincts and to satisfy them by other means than the execution of the physiological acts with a view to which they exist. Love and the instinct of reproduction exist in man before the age of puberty. Canova felt the spur of love at the age of five. Dante was in love with Beatrice at nine; and Byron, then scarcely seven, was already in love with Maria Duff. On the other hand, puberty has no necessary relation to the general maturity of the organism. The family instinct is subject to the same aberrations. Man limits the number of his children. The Turks of to-day follow the ancient Greeks in the practice of abortion. Plato approved of the custom, and Aristotle sanctioned its general prevalence. In the province of Canton the Chinese of the agricultural classes kill two-thirds of their girl children, and the same is done at Tahiti. All these customs co-exist with the perfect love and tender care of the living children. Because of these different discordancies the physical life of man is insufficiently regulated by nature. Neither the physiological instinct, nor the family instinct, nor the social instinct is, in general, sufficiently imperative and precise. Hence, since the internal impulse has not sufficient power, the necessity arises for a rule of conduct exercising its influence from without. Philosophies, religions, and legislation have provided for this. They have regulated man’s hygiene and the carrying out of his different physiological functions. Their control has, moreover, had its hygienic side. The scientific hygiene of to-day has inherited their rôle. The idea of the fundamental perversity of human nature is born of our cognizance of its discordancies, unduly amplified and exaggerated. Soul and body have been considered as distinctly discordant and hostile elements. The body, the shroud of the soul, the temporary host, the prison, the present source of miseries, has been subjected to every kind of mortification. Asceticism has treated the body and all the innate instincts as our mortal foes.