Man associates ideas, not at all in accordance with verifiable exactitude, but with his pleasure and his interest. That is why most truths are merely prejudices. Those that are least open to question are also those that he has always sought to combat cunningly with the ruse of silence. The same inertia is opposed to the work of disassociation seen operating slowly on certain truths. The state of disassociation reached by moral commonplaces seems to bear a rather close relation to the degree of intellectual civilization. Here, too, it is a question of a sort of struggle, carried on, not by individuals, but by peoples formed into nations, against palpable facts which, while augmenting the intensity of the individual life, diminish, for that very reason, as experience proves, the intensity of collective life and energy. There is no doubt that a man can derive from immorality itself--from his refusal to subscribe to the prejudices inscribed in a decalogue--a great personal benefit; but a collectivity of individuals too strong, too mutually independent, makes but a mediocre people. We have, in such cases, the spectacle of the social instinct entering the lists against the individual instinct, and of societies professing, as such, a morality that each of its intelligent members, followed by a very large part of the herd, deems vain, outworn or tyrannical. A rather curious illustration of these principles will be found by examining the present state of sexual morality. This morality, peculiar to Christian peoples, is based upon the exceedingly close association of two ideas--that of carnal pleasure and that of generation. Any man or people that has not disassociated these two ideas, has not mentally liberated the elements of this truth, namely, that outside of the properly generative act, accomplished under the protection of the laws, whether religious or civil--the second being mere parodies of the first, in our essentially Christian civilizations--sexual acts are sins, errors, faults, weaknesses. Whoever consciously adopts this rule, sanctioned by the codes, belongs evidently to a still rudimentary civilization. The highest civilization being that in which the individual is freest, the most exempt from obligations, this proposition would be open to question only if taken as a provocation to libertinism, or as a depreciation of asceticism. It does not matter here whether it be moral or immoral. It ought, if exact, to be seen, at the first glance, in the facts. Nothing is easier. A statistical table of European natality will convince the stubbornest that there is a very close bond--a bond of cause and effect--between a people's intellectuality and its fecundity. The same is true for individuals as for social groups. It is as a result of intellectual weakness that working-men allow their homes to be flooded with offspring. The slums are full of unfortunate individuals who, having begotten a dozen children, are surprised to find life harsh.