Last month, I solicited nominations for a syllabus of forgotten landmarks of American left-wing thought. The responses represented a striking range of works that presaged some of the movement’s lasting and consequential fractures. For example, my initial post was inspired by a re-reading of Herbert Croly, whose writings in the early twentieth century argued that the democratic promise of America could only be fulfilled through nationalized politics and increased federal power. Croly’s project, then, entailed a rebuttal to the separatist and decentralizing strands of American thought, and the positive articulation of a national community. Another popular (if less obscure) nominee—John Dewey—was concerned by this same problem: how could Americans stretch a truly democratic community across such a large, diverse country? But other suggestions illustrated how, by the late 1960s, this project of liberal nation-building was increasingly subject to a searing critique by thinkers who stressed the importance of difference, not commonality. This is a split that has more or less persisted in domestic politics, and the next batch of suggestions indicates another persistent break when it comes to foreign policy.

I noticed this split reflected in reader suggestions. Dana Houle proposed the inclusion of William Appleman Williams, the historian whose critiques of U.S. foreign policy profoundly influenced the New Left view of America as an imperial power. This made an interesting pairing with some suggestions from a historian friend who nominated antifascist writers like Max Lerner, Lewis Mumford, and Archibald MacLeish. Mumford quit The New Republic in 1940 over the magazine’s soft approach to fascism and its reluctance to aid the Allies; MacLeish, a poet, charged the intellectual class with a naïve, detached approach to politics that amounted, in the face of fascism, to unconscionable irresponsibility. The suggestion of Cold War liberals and New Left radicals illustrates a basic split in left-wing foreign policy thought that remains, in some form, today. Part of that split, I suspect, is born of the liberal conviction that government power can be an ameliorative force—an idea with straightforward application in domestic politics (the welfare state), but one which doesn’t map so neatly onto foreign policy.

Here’s where a re-reading of left-wing thought could prove useful, even provocative. The New Left’s legacy on foreign policy is still very much present in intra-left foreign policy disputes. Recent arguments—over whether to intervene in Libya, or what to do about the Syrian civil war, or the rise of ISIS—all reflect its legacy, and, of course, the still-raw memories of the Iraq war. Cold War liberalism doesn’t apply perfectly to contemporary geopolitics, because there’s no contemporary equivalent to the USSR. But it produced a literature of liberals trying to think clearly about the use of U.S power—people who, like their later New Left critics, saw their aim as promoting the democratic self-determination of foreign people. It’s intriguing that this overlap should have produced such different outlooks. Liberals like Mumford and MacLeish insisted that threats would not vanish, and American innocence would not be preserved, by a choice to remain uninvolved in foreign crises. Leftists like Williams insisted that Americans were unjustly sanguine about themselves when they did opt for involvement. That both of these statements can simultaneously be true is a key reason why the fracture has not vanished from left-wing thinking. It’s also a good reason to revisit the arguments that gave birth to it.