Some modern socialists have argued from de Vries's mutation theory in biology that in social evolution we must expect mutations also, and that, therefore, the great changes in human society are normally accomplished by means of revolution. But this argument rests wholly on analogy, and arguments from analogy in science are practically worthless. It may be asserted, on the other hand, that all the great changes in human society which have been desirable have come about only after prolonged preparation and after a series of gradual steps which led up to the final change. The Greco-Roman world, for example, was becoming ripe for Christianity before Christianity finally appeared and became triumphant. The centuries from the fourteenth to the sixteenth had prepared for the protestant reformation in the countries of modern Europe before the reformation became an established fact. Thus, radical reconstruction of the social life by means of revolution is scarcely possible. The instincts and habits of individual human nature upon which the social order rests cannot be easily changed by revolutionary programs in legislation or in institutions. The only probable result of such an attempt would be the collapse of the new social order, because it would have insufficient foundations in individual character upon which to rest. The idea of ushering in the social millennium through some vast social revolution is therefore chimerical. It is not the place in this book to take up the practical objections to economic socialism. These practical objections are for the most part of a political and economic nature, and they accordingly can be better dealt with in treatises on politics and economics than in one on sociology. It is perhaps sufficient to say that the political and economic objections to socialism are not less weighty than the sociological objections. Government, for example, exists in human society to regulate, and not to carry on directly, all social activities. If the state were in its various forms called upon to own and manage all productive wealth in society, it is extremely probable that such an experiment would break down of its own weight, since the state would be attempting that which, in the nature of things, as the chief regulative institution of society, it is not fitted to do. But it is not our purpose, as has just been said, to go into the political and economic objections to economic or Marxian socialism. To understand these the student must consult the leading works on economic and political science.