It is equally clear that if a mother is to act morally with regard to her child, she must teach herself properly. In place of mythology and literature, she must learn hygiene and all that relates to the rational rearing of children. So, also, in the education of men, the study of the exact sciences must occupy by far the most important place. Then only will moral conduct and scientific knowledge begin to unite. An ignorant mother will bring up a child very badly notwithstanding all her good will and her affection. A doctor, however imbued with strong sympathy for his patients, could do them much harm if he had not the appropriate knowledge. Are not politicians open to the reproach from the point of view of morality that very often through ignorance they do the very worst evil in public administration? With the progress of knowledge, moral conduct and useful conduct will become more and more closely identified. I have been reproached because in my system the health of the body occupies too large a place. It cannot be otherwise, because health certainly plays the chief part in existence. Notwithstanding his pessimism, Schopenhauer was convinced that health was the greatest treasure, a treasure before which everything else yielded. In many religions care of the health is laid down amongst the chief duties. Although many scientific men do not hold the opinion that circumcision was ordained for hygienic reasons, it is certain that hygiene was extremely important in the Jewish religion. It is only in Christianity, which despises the human body, that hygiene is excluded from the religious code, as in the words of Jesus:- “Take no thought for your life, what ye shall eat, or what ye shall drink; nor yet for your body, what ye shall put on. Is not the life more than meat, and the body than raiment?” (Matt. vi., 25). As for long ages hygiene was very imperfectly known, it is not surprising that it played a small part in human affairs. Probably the objection to the importance that I assign to it in orthobiosis is a relic from the old order of things. Now, however, the situation is different. Bacteriology has placed hygiene on a scientific foundation, so that the latter is now one of the exact sciences. It has now become necessary to give it the chief place in applied morality as it is the branch of knowledge that teaches how men ought to live.