Marx and Engels always defended philosophical materialism in the most determined manner and repeatedly explained the profound error of every deviation from this basis. He enriched it with the acquisitions of German classical philosophy, especially of the Hegelian system, which in its turn led to the materialism of Feuerbach. Deepening and developing philosophical materialism, Marx completed it, extended its knowledge of nature to the knowledge of human society. Marx's historical materialism was one of the greatest achievements of scientific thought. The chaos and arbitrariness that had previously reigned in the views on history and politics gave way to a strikingly integral and harmonious scientific theory, which shows how, in consequence of the growth of productive forces, out of one system of social life another and higher system develops-how capitalism, for instance, grows out of feudalism.
Political institutions are a superstructure on the economic foundation.
We see, for example, that the various political forms of the modern European states serve to fortify the rule of the bourgeoisie over the proletariat. Marx's philosophy is matured philosophical materialism, which has provided humanity, and especially the working class, with powerful instruments of knowledge. Having recognized that the economic system is the foundation on which the political superstructure is erected, Marx devoted most attention to the study of this economic system. Marx's principal work, Capital , is devoted to a study of the economic system of modern, i.e., capitalist, society. Classical political economy, before Marx, evolved in England, the most developed of the capitalist countries.