The foregoing is the case of an action in conformity with the ideal, but quite contrary to human nature as it is at present. A similar contradiction appears in reproduction. Man came from animals amongst which unlimited reproduction was an important factor in the preservation of the species, as it allowed the species to survive under all sorts of bad conditions, such as diseases, combats, attacks of enemies, and changes of climate. Although man, according to the laws of human nature, is capable of reproducing extremely rapidly, the ideal of his happiness makes a restriction of this power necessary. Thus orthobiosis, based upon knowledge of human nature, would set limits to a function which is perhaps the most natural of all. The restriction which is already partially adopted will come more and more into operation as the struggle against diseases, the prolongation of human life, and the suppression of war make progress. It will be one of the chief means of diminishing the most brutal forms of the struggle for existence, and of increasing moral conduct amongst mankind. Just as Rimpau began to study the nature of plants before trying to realise his ideal, so also varied and profound knowledge is the first requisite for the ideal of moral conduct. It is necessary not only to know the structure and function of the human organism, but to have exact ideas on human life as it is in society. Scientific knowledge is so indispensable for moral conduct that ignorance must be placed among the most immoral acts. A mother who rears her child in defiance of good hygiene, from want of knowledge, is acting immorally towards her offspring, notwithstanding her feeling of sympathy. And this also is true of a Government which remains in ignorance of the laws which regulate human life and human society.