In his doctoral dissertation on Epikur and Demokrit, written in 1840–1841, Marx tried to show against the prevailing scientific opinion that Epikur had a very different philosophy of nature compared with Demokrit, the materialist determinist. In Marx’ view, Epikur was much superior to Demokrit in that he was a sceptical and non-dogmatic philosopher who did not try to develop an objective philosophy of nature. For Epikur, knowledge of nature had only the function to improve the ataraxy of human self-consciousness; against the principle of determination he put chance and accident, leaving room for human free choice which is influenced by human drives and desires and the so-being of the surrounding nature. The feeling of repulsion and dependency of something in us and out there leads to a dialectical insight of our relativity and relatedness and ends positively in a Aufhebung of the polar concepts and antinomy of human free will vs. objective determination (EB, pp. 257 ff.).
For Marx – and this is the genuine and simple materialist aspect of his thinking – the fundamental question confronting all human societies concerns what we must do to survive as living beings with an energy consuming body. To live, we must combine our intelligence and our energy (our work) with the basic “materials” of the world we find ourselves in, its water, soil and air. For Marx, nature is the organic body of man. We must work with what is at hand in order to make this today into tomorrow. The economic organization of society, or the “mode of production”, is therefore for him the most powerful force in determining the structure of human society. Today this Marxian basic principle sounds more self-evident and insofar we can say that we are all more or less Marxists now. But at Marx’ time even Feuerbach’s critique of Hegel’s idealism was only a theological one.