The proletarian class struggle existed before Marx for it is the offspring of capitalist exploitation. It was nothing more than natural that the workers, being exploited, should think about and demand another system of society where exploitation would be abolished. But all they could do was to hope and dream about it. They were not sure of its coming to pass. Marx gave to the labor movement and Socialism a theoretical foundation. His social theory showed that social systems were in a continuous flow wherein capitalism was only a temporary form. His studies of capitalism showed that owing to the continuous development of perfection of technique, capitalism must necessarily develop to Socialism. This new system of production can only be established by the proletarians struggling against the capitalists, whose interest it is to maintain the old system of production. Socialism is therefore the fruit and aim of the proletarian class struggle. Thanks to Marx, the proletarian class struggle took on an entirely different form. Marxism became a weapon in the proletarian hands; in place of vague hopes he gave a positive aim, and in teaching a clear recognition of the social development he gave strength to the proletarian and at the same time he created the foundation for the correct tactics to be pursued. It is from Marxism that the workingmen can prove the transitoriness of capitalism and the necessity and certainty of their victory. At the same time Marxism has done away with the old utopian views that Socialism would be brought about by the intelligence and good will of some judicious men; as if Socialism were a demand for justice and morality; as if the object were to establish an infallible and perfect society. Justice and morality change with the productive system, and every class has different conceptions of them. Socialism can only be gained by the class whose interest lies in Socialism, and it is not a question about a perfect social system, but a change in the methods of production leading to a higher step, i. e., to social production. Because the Marxian theory of social development is indispensable to the proletarians in their struggle, they, the proletarians, try to make it a part of their inner self; it dominates their thoughts, their feelings, their entire conception of the world. Because Marxism is the theory of social development, in the midst of which we stand, therefore Marxism itself stands as the central point of the great mental struggles that accompany our economic revolution. IV. DARWINISM AND THE CLASS STRUGGLE.