He draws the conclusion from these data that strenuous intellectual energy is much more unfavourable than hard physical labour to the production of ability in the offspring. Intellectual workers, therefore, he argues, must have their children when young, and we must so modify our social ideals and economic conditions as to render this possible. That the mother should be equally young is not, he holds, necessary; he finds some superiority, indeed, provided the father is young, in somewhat elderly mothers, and there were no mothers under twenty-three. The rarity of genius among the offspring of distinguished parents is attributed to the unfortunate tendency to marry too late, and Vaerting finds that the distinguished men who marry late rarely have any children at all. Speaking generally, and apart from the production of genius, he holds that women have children too early, before their psychic development is completed, while men have children too late, when they have already "in the years of their highest psychic generative fitness planted their most precious seed in the mud of the street." The eldest child was found to have by far the best chance of turning out distinguished, and in this fact Vaerting finds further proof of his argument. The third son has the next best chance, and then the second, the comparatively bad position of the second being attributed to the too brief interval which often follows the birth of the first child. He also notes that of all the professions the clergy come beyond comparison first as the parents of distinguished sons (who are, however, rarely of the highest degree of eminence), lawyers following, while officers in the army and physicians scarcely figure at all. Vaerting is inclined to see in this order, especially in the predominance of the clergy, the favourable influence of an unexhausted reserve of energy and a habit of chastity on intellectual procreativeness. This is one of his main conclusions.