This article intends to show, from an analysis of two important passages from Theories of Surplus Value and Capital, Marx's criticism of Ricardo and his epistemological precariousness. According to Marx, Ricardo's conceptual confusions are due to the fact that he does not carry on the abstraction process and thought purification beyond the deceiving interferences of competition as well as the dogmas and vulgar representations of the practical capitalist. For Marx, the truly scientific thought is thinking which raises itself above those falses representations and thinks the true as a thinking activity, not as a representation or a sensible intuition activity.2026183199