When he becomes adult, man experiences the instinctive need of relations with someone of the other sex. This need lays certain duties on him, and although the love of a young man is less egoistical than that of the child, it is far from presenting the characters of self-abnegation and sacrifice. A young woman, after having passed through the usual cycle of life with her mother and with a man, becomes herself a mother. Maternal instinct furnishes her with certain rules of conduct, but this natural instinct is not enough to fulfil its object, that is to say, to rear the child until an age when it can live independently. Directed by a feeling of sympathy for her child, the young mother learns from women with more experience to ward off dangers from her child. In the first years, moral conduct on the part of the mother consists almost entirely in bringing up the child in a healthy way. For this purpose she must acquire much knowledge. If she remains ignorant, her conduct must be regarded as immoral. So far as concerns the bringing up of a child, the moral problem is quite simple, because we are all agreed that the object is to rear the child to maturity in the healthiest possible condition. When the child exhibits any habits harmful to this object, although due to natural instincts, the mother applies her knowledge to restrain them without paying attention to the theory that happiness consists in the fulfilment of everything that is natural. When a child has passed through the perilous first period of its life, the mother has to ask what general object she is to follow in its education. She wishes her child to be as happy as possible. Here the conception of orthobiosis will serve her, and it will teach her that the greatest happiness consists in the normal evolution of the sense of life, leading to serene old age, and finally reaching the fulness of satiety of life. Man, who has passed his apprenticeship to life from his birth, with his protectors, and, later on, with persons of the other sex, inevitably acquires certain elements necessary for social life. Persuaded that in order to succeed in his individual life he must have help from his fellows, he learns to subdue his anti-social tendencies, at first in his own interests. Let me take an example of this. When a man has reached a certain stage of civilisation, it generally becomes impossible to him to supply his bodily wants without the help of persons less cultured than himself. He takes into his house one or more servants, with whom he enters into definite relations. He wishes for himself and those about him a normal life, such as I have described in _The Nature of Man_. To attain this it is indispensable in his own interest and in that of his family, that his domestic servants should be well treated. The health of the family very often depends on the conduct of the servants, who will follow conscientiously the hygienic rules only if they themselves are living in good conditions. The custom