The interpretation of the doctrine of historical materialism presented a number of difficulties deriving partly from the form in which the doctrine itself had originally appeared--not as a coherent theory, but as a series of pronouncements and observations scattered in a variety of writings, composed at a distance of years, and the aim of which was rather political and polemical than scientific; and partly from its association with remnants of old metaphysics, both in its originators and in their followers. In Marx and Engels, as well as practically in the whole literature of Marxism, the emphasis being laid on the substantive rather than on the adjective, historical materialism implied the adhesion to that metaphysical materialism which was one of the children of Hegelian metaphysics. What had been the Idea for Hegel, was the Economy of the new metaphysicians: the only reality, working beneath the surface of human consciousness, as an under-structure beneath a merely apparent and illusory superstructure. Given this conception, it is easy to understand why historical materialism appealed so strongly to positivists and evolutionists, who concealed a similar kind of metaphysics under their proclaimed contempt for philosophy. The old philosophies of history had attempted to reduce the sequence of history to a scheme of concepts, starting with God, or Providence, or the Hegelian Idea: the new unconscious metaphysicians substituted for the old concepts that of Economy, or of Matter, or of Development and Evolution, from which all the particular historical determinations could be deduced with not less certainty than from the old metaphysical entities. And from their predecessors they also borrowed those teleological tendencies which are implicit in all metaphysics, attributing a will and an end to their new God, be it called Progress or Matter, and trying to deduce the future course of history from the dialectic of the past. Hence the growth of a vast literature inquiring into the development of abstract sociological schemes or of economic forms reduced to characteristics of economic epochs, forcing the concrete materials of history into rigid conceptual frames; hence the naïve faith in the deduction of social predeterminations, of which the most striking was the asserted necessity of the advent of socialism as the only logical outcome of capitalist society.