Selfishness is not an ultimate ethical conception; the more it is analysed, the vaguer it becomes. But as a phenomenon in the nursery it is perfectly definite, and presents problems with which it is very necessary to cope. Left to himself, an older child will seize a younger child’s toys, demand more than his share of grown-up attention, and generally pursue his desires regardless of the younger child’s disappointments. A human ego, like a gas, will always expand unless restrained by external pressure. The object of education, in this respect, is to let the external pressure take the form of habits, ideas and sympathies in the child’s own mind, not of knocks and blows and punishments. The idea which is needed is that of justice, not self-sacrifice. Every person has a right to a certain amount of room in the world, and should not be made to feel wicked in standing up for what is due to him. When self-sacrifice is taught, the idea seems to be that it will not be fully practised, and that the practical result will be about right. But in fact people either fail to learn the lesson, or feel sinful when they demand mere justice, or carry self-sacrifice to ridiculous extremes. In the last case, they feel an obscure resentment against the people to whom they make renunciations, and probably allow selfishness to return by the back door of a demand for gratitude. In any case, self-sacrifice cannot be true doctrine, because it cannot be universal; and it is most undesirable to teach falsehood as a means to virtue, because when the falsehood is perceived the virtue evaporates. Justice, on the contrary, can be universal. Therefore justice is the conception that we ought to try to instil into the child’s thoughts and habits.