Knowledge wielded by love is what the educator needs and what his pupils should acquire. In earlier years, love towards the pupils is the most important kind; in later years, love of the knowledge imparted becomes increasingly necessary. The important knowledge at first is knowledge of physiology, hygiene, and psychology, of which the last more especially concerns the teacher. The instincts and reflexes with which a child is born can be developed by the environment into the most diverse habits, and therefore into the most diverse characters. Most of this happens in very early childhood; consequently it is at this period that we can most hopefully attempt to form character. Those who like existing evils are fond of asserting that human nature cannot be changed. If they mean that it cannot be changed after six years old, there is a measure of truth in what they say. If they mean that nothing can be done to alter the instincts and reflexes with which an infant is born, they are again more or less in the right, though of course eugenics could, and perhaps will, produce remarkable results even here. But if they mean, as they usually do, that there is no way of producing an adult population whose behaviour will be radically different from that of existing populations, they are flying in the face of all modern psychology. Given two infants with the same character at birth, different early environments may turn them into adults with totally different dispositions. It is the business of early education to train the instincts so that they may produce a harmonious character, constructive rather than destructive, affectionate rather than sullen, courageous, frank, and intelligent. All this can be done with a great majority of children; it is actually being done where children are rightly treated. If existing knowledge were used and tested methods applied, we could, in a generation, produce a population almost wholly free from disease, malevolence, and stupidity. We do not do so, because we prefer oppression and war.