This paper is forthcoming in an issue of the leading European journal devoted to the Frankfurt School, Analyse und Kritik, in a special issue on an important topic in Marxist theory, namely, "The Normative Turn Away from Marxism."  The abstract:

Marx did not have a normative theory, that is, a theory that purported to justify, discursively and systematically, his normative opinions, to show them to be rationally obligatory or objectively valid.  In this regard, Marx was obviously not alone:  almost everyone, including those who lead what are widely regarded as exemplary “moral” lives, decide and act on the basis of normative intuitions and inclinations that fall far short of a theory.  Yet self-proclaimed Marxists like G.A. Cohen and Jurgen Habermas have reintroduced a kind of normative theory into the Marxian tradition that Marx himself would have ridiculed.  This essay defends Marx’s position and tries to explain the collapse of Western Marxism into bourgeois practical philosophy, i.e., philosophizing about what ought to be done that is unthreatening to capitalist relations of production (more precisely, practical philosophy that is addressed to individuals, that is primarily concerned with what to believe, and that is obsessed with moral trivialities).  

Part I argues that the Marxian account of revolution under capitalism presupposes only that the agents are instrumentally rational (and thus Marx is, for all important purposes, a Humean).  Part II offers a kind of intellectual genealogy of the rise of bourgeois practical philosophy in America, England, and Europe, focusing, in particular, on Cohen and Habermas, but also Peter Singer.  Various forms of intuitionism (Moore, Rawls) are central to the story in the Anglophone world, while the crucial event in the European context was the merely philosophical challenge to instrumental rationality launched by Horkheimer and brought to Kantian fruition by Habermas. 

Part III concludes with some speculative structural hypotheses about why Marxism should have collapsed into irrelevant normative theory over the last half-century, noting the political and legal purge of Marxists in both American and Germany, as well as the massive expansion of the university system and the premium placed on an appearance of a “method.”