There is a paradox about the inroads socialism has made in American political discourse in the past five years, thanks to Senator Bernie Sanders’s presidential candidacies. Not in many lifetimes, and perhaps never, has socialism figured so prominently in American political rhetoric. But theories of what socialism really means are hard to come by — especially when its advocates claim the mantle of Karl Marx, the granddaddy of all socialist thinkers, as so many socialist intellectuals and movements did for a century and more.

The deaths in succession of Moishe Postone in March 2018 and Erik Olin Wright in January 2019 were symbolic in this sense. Of the generation of great intellectuals whose 1960s experiences led them to adopt a lifework of recovering and reimagining Marxism, next to nobody is left. The last of the Mohicans, perhaps, is Perry Anderson, industrious and loquacious as ever — but many years ago he moved on to writing country studies and intellectual profiles. The New Left Review that he founded proceeds in his spirit without the raucous theoretical disputation it once hosted in the 1970s. Jacobin, an extraordinary thing for all American socialists, millennial and not, tends to avoid descent into in-house argument about the deepest premises of its political agenda. Due to its work, and the dereliction of the world, many young Americans have lost trust in their elders who built a rotten society, and dream of its replacement. Even as practical ideas teem, however, the tradition of “Marxist theory” seems dead and buried.

Should it stay that way? After all, Karl Marx himself counseled, in the most memorable of his Theses on Feuerbach, that philosophers had only ever interpreted the world; the point, however, is to change it. The insistent orientation toward policy and practical matters among today’s American socialists, for whom the Green New Deal is more important to fight about than the Grundrisse, is worthwhile. Yet for those who have studied in the history of socialism in general and Marxism in particular, this orientation is likely to reach limits, especially when big choices beckon. What does one mean when one says one is a socialist? If you are a Marxist, what kind? What is capitalism, and what is the socialist alternative?