"For the fundamental fact of human psychology is that society, instead of remaining almost entirely inside the individual organism as in the case of animals prompted by their instincts, becomes crystallized almost entirely outside the individuals. In other words, social rules, as Durkheim has so powerfully shown, whether they be linguistic, moral, religious, or legal, etc., cannot be constituted, transmitted or preserved by means of an internal biological heredity, but only through the external pressure exercised by individuals upon each other."