
These deep-rooted affinities are normally passed over in pious silence; they nevertheless constitute, from Epicurus to Spinoza and Hegel, the premises of Marx's materialism. They are hardly ever mentioned, for the simple reason that Marx himself did not mention them, and so the whole of the Marx-Hegel relationship is made to hang on the dialectic, because this Marx did talk about!
Louis Althusser, Essays in Self-Criticism (1976), "Is it Simple to be a Marxist in Philosophy?"
A - F, Louis Althusser