A peculiar mix of political extremism and ideological malaise characterizes post-2016 American politics. While factions abound, few of them have anything new to say. Instead, the most outré cliques on both the left and the right have resorted to nostrums that reached the height of their appeal in the middle of the last century. It is as if everyone showed up to a party wearing their parents’ ill-fitting hand-me-downs.

Nowhere is this intellectual stagnation more obvious than in discussions of class. The only contemporary right-wing intellectuals to explicitly recognize the existence of an American class system—the nationalist conservatives—seem to have pillaged their rhetoric of globalist elites and common folk from anti-Dreyfusard pamphlets and even more unsavory German sources. Meanwhile, class discourse on the left tends to revolve around the categories inherited from Marx: proletariat and bourgeoisie, labor and capital.

To say that Marx’s class schema has lost some of its salience is not to suggest that class has become irrelevant. The economic class structure in the United States is more rigid—and the distance between the upper and lower classes vaster—than at any point in the past 80 years, if not longer. But the categories that the US left most often uses have lost some of their purchase. The connection between one’s class and one’s relationship to the means of production seems to have been partially severed, such that people with similar salaries and job descriptions—perhaps even colleagues performing equivalent functions in a shared workplace—may have dramatically different class backgrounds and economic prospects. We need new categories to explain why.

Here, Marx still has something timely to say—not so much in his typology of class as in the method he used to arrive at it. Recall that he developed his theory while watching the emergence of a new class, the urban industrial proletariat. By tracing the development of new social classes, we can better understand how our world has changed and what that means. Following Marx’s example, we should look for distinct social classes that have emerged in the postindustrial era. Doing so will help us identify the driving force behind modern inequality. An ideal subject for investigation would be one that, like the urban proletariat of the industrial age, sits near the bottom of the economic ladder but has become a major political concern for members of all other classes. Such a class would also need to be recognizably new. Our strongest candidate is a group that we have come to call the homeless.

Although poor Americans have always resided in substandard housing, street homelessness only became a large-scale urban phenomenon in the late 1970s. A relatively early study of the homelessness crisis, Peter Rossi’s Down and Out in America, distinguishes between “old” homelessness and contemporary “literal homelessness” by noting that in the decades prior to the rise of mass homelessness, “the homeless by and large were familyless persons living in very inexpensive (and often inadequate) housing, mainly cubicle and SRO [single-room-occupancy] hotels.” By 1979, Rossi wrote, “It became more and more difficult to ignore the evidence that some people had no shelter and lived on the streets.” (Under the current definition used by the federal government, many SRO and cubicle hotel residents would not be considered homeless.)