This article discusses the methodological aspects of Marx’s theoretical approach. It draws on the epistemology of Gaston Bachelard, and especially on the interpretation of Louis Althusser. It examines in detail Bachelard’s concepts of connaissance commune and epistemological rupture, and also Althusser’s distinction between “Generalities I” and “Generalities III”, while putting these concepts into the context of Marx’s critique of political economy. A significant focus here is also the distinction between “real object” and “the object of knowledge”, as well as the concepts of Darstellung, structural causality and overdetermination (surdétermination). The article demonstrates that Marx’s method of the historicising and denaturalising theoretical categories can be an effective instrument in de-ideologising the areas which Althusser characterises as “theoretical ideology”.