"To Hegel, the life-process of the human brain, i.e. the process of thinking, which, under the name of ‘the Idea’, he even transforms into an independent subject, is the demiurgos of the real world, and the real world is only the external, phenomenal form of ‘the Idea’. With me, on the contrary, the ideal is nothing else than the material world reflected by the human mind, and translated into forms of thought."
Karl Marx (Capital, Afterword, Second German Ed., Moscow, 1970, vol. 1, p. 29)