It is now very long since there has been opportunity for the heroism which steeled the hand of Abraham to sacrifice his only son to his religion. Human sacrifice, based on the highest morality, has become more and more rare, and will finally disappear. Rational morality, although it may admire such conduct, has no use for it. So also, it may foresee a time when men will be so highly developed that instead of being delighted to take advantage of the sympathy of their fellows, they will refuse it absolutely. Neither the Kantian idea of virtue, doing good as a pure duty, nor that of Herbert Spencer, according to which men have an instinctive need to help their fellows, will be realised in the future. The ideal will rather be that of men who will be self-sufficient and who will no longer permit others to do them good. IV ORTHOBIOSIS Human nature must be modified according to an ideal—Comparison with the modification of the constitution of plants and of animals—Schlanstedt rye—Burbank’s plants—The ideal of orthobiosis—The immorality of ignorance—The place of hygiene in the social life—The place of altruism in moral conduct—The freedom of the theory of orthobiosis from metaphysics As I have shown in _The Nature of Man_, the human constitution as it exists to-day, being the result of a long evolution and containing a large animal element, cannot furnish the basis of rational morality. The conception which has come down from antiquity to modern times, of a harmonious activity of all the organs, is no longer appropriate to mankind. Organs which are in course of atrophy must not be reawakened, and many natural characters which perhaps were useful in the case of animals must be made to disappear in men. Human nature, which, like the constitutions of other organisms, is subject to evolution, must be modified according to a definite ideal. Just as a gardener or stock raiser is not content with the existing nature of the plants and animals with which he is occupied, but modifies them to suit his purposes, so also the scientific philosopher must not think of existing human nature as immutable, but must try to modify it for the advantage of mankind. As bread is the chief article in human food, attempts to improve cereals have been made for a very long time. Rimpau made one of the greatest steps in this direction when he introduced into cultivation a variety of rye known as Schlanstedt rye, now fairly abundant in France and Germany. Rimpau set himself the task of producing a variety with the longest ears and containing many and heavy grains. Having conceived his ideal, he began to seek out what was nearest to it in a very large number of examples of rye. After patient and continued labour, using careful selection and cross-fertilisation, Rimpau succeeded in making the new variety, and so did a great service to mankind.