It is in this sense that Galileo accomplished a scientific revolution; for he did not confine himself to reforms of the astronomical system received in his time, but he radically changed its fundamental lines. And it is in this same sense that Jacquart effected an industrial revolution, since he did not confine himself to reforming the hand-loom, as it had existed for centuries, but radically changed its structure and productive power. Therefore, when socialists speak of socialism as _revolutionary_, they mean by this to describe the programme to be realized and the final goal to be attained and not--as M. Garofalo, in spite of the dictionary, continues to believe--the method or the tactics to be employed in achieving this goal, the social revolution. And right here appears the profound difference between the method of sentimental socialism and that of scientific socialism--henceforth the only socialism in the civilized world--which has received through the work of Marx, Engels and their successors that systematic form which is the distinctive mark of all the _evolutionary_ sciences. And that is why and how I have been able to demonstrate that contemporary socialism is in full harmony with the scientific doctrine of evolution. Socialism is in fact evolutionary, but not in the sense that M. Garofalo prefers of "waiting patiently until the times shall be ripe" and until society "shall organize _spontaneously_ under the new economic arrangement," as if science necessarily must consist in Oriental contemplation and academic Platonism--as it has done for too long--instead of investigating the conditions of actual, every-day life, and applying its inductions to them. Certainly, "science for the sake of science," is a formula very satisfactory to the avowed conservatives--and that is only logical--and also to the eclectics; but modern positivism prefers the formula of "science for life's sake" and, therefore, thinks that "the ripeness of the times" and "the new economic arrangement" will certainly not be realized by spontaneous generation and that therefore it is necessary to act, in harmony with the inductions of science, in order to bring this realization to pass. To act, but _how_? There is the question of methods and tactics, which differentiates utopian socialism from scientific socialism; the former fancied it possible to alter the economic organization of society from top to bottom by the improvised miracle of a popular insurrection; the latter, on the contrary, declares that the law of evolution is supreme and that, therefore, the social revolution can be nothing but the final phase of a preliminary evolution, which will consist--through scientific study and propaganda work--in the realization of the exhortation of Marx: _Proletarians of all countries, unite!_