Forget for a moment about the ideological divisions between liberals and conservatives, socialists and capitalists, populists and establishmentarians. The fissure that is likely to have far more of an impact on our future is the one separating those who warmly support nationalism from those who stringently reject it.

In the popular imagination and conventional wisdom, the debate between nationalists and their globalist opponents mirrors the ideological clashes of the past, with the former falling on the right and the latter leaning to the left. While that's sometimes the case, it isn't always. The real distinction is between political analysts and actors who recognize and respect the importance of fostering social cohesion at the national level as a precondition of pursuing other social goods and those who deny the importance of such cohesion and even reject its legitimacy on moral grounds. Those who affirm the need to foster cohesion can be found on either the right or the left, and their critics can as well.

Consider recent books by three of our sharpest political thinkers: Yoram Hazony's The Virtue of Nationalism; Reihan Salam's Melting Pot or Civil War?; and John Judis' The Nationalist Revival. Hazony is a conservative Israeli writer and political theorist; Salam is a conservative public policy analyst and executive editor of National Review; and Judis is a journalist and longstanding advocate for the left. All three have important things to say about the crucial importance of social cohesion and the dangers of losing it.

Hazony's cogently argued book takes aim at two targets: classical liberals in the tradition of Thomas Hobbes and John Locke, who treat politics as an arrangement devised and consented to by individuals; and modern liberals, who view expressions of communal solidarity at the level of the nation with disdain and elevate universalistic internationalism as vastly preferable in moral terms.

For Hazony, classical liberalism fails to recognize both that communal attachments are more primary than individual pursuits and that many of the most enduring and valuable human goods are products of those attachments. Modern liberalism, meanwhile, fails to appreciate the great advantages of the order of free and independent nation states that emerged from the Treaty of Westphalia in mid-17th-century Europe. Instead, these modern liberals prefer a form of (benignly intended) imperialism that seeks to impose its own moral, political, and economic vision on the nations of the world as it spreads across the globe, ultimately aiming to expand indefinitely (as, on Hazony's telling, all forms of imperialism tend to do). In place of these forms of liberal individualism and imperialism, Hazony advocates a world in which the many "virtues of nationalism" laid out in his book are recognized and appreciated.

Salam is less interested in the theoretical speculations and proscriptions that fill Hazony's pages. With his eyes fixed much closer to the ground of concrete policy prescriptions within the United States, Salam (himself the son of Bangladeshi immigrants) makes a powerful case for two significant changes in the way Americans think about and manage their borders. In place of the family-based immigration of recent decades, in which members of the same (often very poor) family sponsor and then follow one another to the U.S. over time, Salam proposes to shift toward skills-based immigration in which annual quotas and limits would be set based on the needs of specific segments of the economy. Then there is the goal of assimilation — captured in the classic metaphor of the melting pot — which Salam persuasively argues we need to revive and enforce.

Both reforms would help to forestall a further breakdown of social cohesion (the "civil war" in Salam's somewhat sensationalistic title) — the first by assuring that immigrants are more quickly and fully integrated into the country's economy, the second by assuring that immigrants are more quickly and fully integrated into the country's culture. The alternative to such integration isn't a multicultural paradise of thriving groups living happily alongside one another so much as a national community badly fraying, with increasingly "racialized" immigrants squaring off against increasingly hostile native-born Americans, and the broad-based support needed for projects and policies of national scope collapsing along with social trust and solidarity.

The latter is Judis' primary concern in both his book and a recent New York Times op-ed. In both he makes a strong case that "a common national identity is essential to democracies and to the modern welfare state, which depends on the willingness of citizens to pay taxes to aid fellow citizens whom they may never have set eyes upon." Neglect of this fundamental truth has been accompanied by an embrace among many on the left of a "utopian cosmopolitanism" that "advocates open borders, free trade, rampant outsourcing, and has branded nationalist sentiments as bigotry."

This has fueled an extreme reaction on the part of many working people, at home and abroad, who have turned to right-wing demagogues like our president as the only figures willing to champion national solidarity without shame or apology. Much better would be for the left to make the case for its preferred policies in terms of communal solidarity and national fellow-feeling — to work with instead of against "the nationalist reaction to globalization."

Which isn't to say that the nationalists aren't plagued by difficulties of their own. There's a reason that the nationalist appeals of President Trump and his analogues abroad invariably provoke polarization and division instead of unity — because social cohesion and trust have already collapsed to such an extent, with our highly diverse national communities already so fractured, that efforts to bring us all together end up making things worse, raising seemingly intractable questions about who exactly "we" even are. It may even be that the longing for, and awareness of the need for, national unity tends to become most powerful only when such unity has already vanished and fallen beyond our grasp.

But that doesn't mean that the problems diagnosed by those on the nationalist side of the debate can be willed or wished away. On the contrary, it could be that these problems will remain and only get worse over time — with the country desperately needing to undertake a drastic change of direction while lacking anything approaching the consensus, trust, and solidarity that would be necessary to decide resolutely on what the direction should be, let alone to exert the collective effort required to accomplish it.