EDITOR’S NOTE: This article is part of The Nation’s special issue on Barack Obama’s presidency, available in full here.

Last spring, I taught my final class at Columbia University, and now I’m riding off into the sunset of retirement. The course, which attracted some 180 students, was called “The American Radical Tradition.” Beginning with the American Revolution, it explored the ideas, tactics, strengths, weaknesses, and interconnections of the movements that have attempted to change American society—from abolitionism and feminism to the labor movement, socialism, communism, black radicalism, the New Left, Occupy Wall Street, and Black Lives Matter. Although the word “radicalism” is often applied to those on the right as well as the left, I announced at the outset that since we had only one semester, I planned to focus on what might be called left-wing radicalism. Those students who wanted exposure to right-wing radicalism, I added, could enroll in any class in Columbia’s business school.

Teaching the class as Barack Obama’s presidency neared its end and Senator Bernie Sanders’s campaign ignited the enthusiasm of millennials was an interesting experience. I began with the premise that radicalism has been a persistent feature of our history and that radicals, while often castigated as foreign-inspired enemies of American institutions, have usually sprung from our culture, spoken its language, and appealed to some of our deepest values—facts that help to explain radicalism’s persistence even in the face of tenacious opposition. American radicalism entails a visionary aspiration to remake the world on the basis of greater equality—economic, legal, social, racial, or sexual. Despite the occasional resort to violence, most of these movements have reflected the democratic ethos of American life: They’ve been open rather than secretive and have relied on education, example, or political action rather than coercion. Not surprisingly, they have also reflected some of the larger society’s flaws; radicals are a product of their society, no matter how fully they reject certain aspects of it. While I made clear my sympathy with most of the groups we studied, I also insisted that we should not be surprised that some abolitionists were antifeminist, some feminists racist, some labor organizations hostile to immigrants. Neither history nor politics is well served by simple hagiography.

From Thomas Paine’s ideal of an America freed from the hereditary inequalities of Europe, to the vision of liberation from legal and customary bondage espoused by abolitionists and feminists; from the Knights of Labor’s concept of a cooperative commonwealth, to the socialists’ call for workers to organize society in accordance with their own aspirations; from the New Left’s embrace of personal liberation as a goal every bit as worthy as material abundance, to the current efforts to counteract the less appealing consequences of globalization, each generation has made its distinctive contribution to an ongoing radical tradition. Many achievements that we think of as the most admirable in our history are to a considerable extent the outgrowth of American radicalism, including the abolition of slavery, the dramatic expansion of women’s rights, the respect for civil liberties and our right of dissent, and the efforts today to tame a rampant capitalism and combat economic inequality. Many of our current ideas about freedom, equality, and the rights of citizens originated with American radicals.

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More than any other movement, I told my students, abolitionism provided the template for how to achieve radical change in America. The abolitionists’ first task was to destroy the conspiracy of silence by which political parties, churches, and other institutions sought to exclude slavery from public debate. While differing among themselves on strategy and tactics, abolitionists understood that radical change requires the cooperation of an engaged social movement and enlightened political leadership. Long after the Civil War, organized labor, Populists, advocates of women’s rights, and many other radical activists looked to the crusade against slavery as an inspiration and a model, and in slogans like “wage slavery” and “the slavery of sex” adapted its language to their own concerns. I also devoted a good deal of time to the long struggle for women’s equality and how it challenged fundamental aspects of American society, including the idea of “separate spheres” for men and women; the doctrine of coverture, whereby a married women’s legal identity was subsumed into her husband’s; and the demarcation of the family as a site insulated from questions of power, rights, and oppression.

Obama’s 2008 campaign, which mobilized millions of people new to politics, served as an illustration of the symbiotic relationship between popular movements and political action. Unfortunately, even before Obama assumed office, it became clear that he had little interest in building upon the popular upsurge that helped to elect him. A revealing moment came at a press conference at the end of November 2008, when he was asked how he reconciled his campaign slogan, “Change We Can Believe In,” with the appointment of an economic team largely composed of the same neoliberal ideologues who had helped bring about the financial crisis. “The vision for change,” Obama replied, “comes…first and foremost…from me.” As I mentioned to my class, one can compare Obama’s top-down remark to a comment attributed to the early-20th-century socialist Eugene Debs: “I would not lead you to the promised land if I could, because if I could lead you in, someone else could lead you out.”

Debs understood that movements, not just political leaders, make social change possible. Obama has never really learned that lesson. To be sure, he sought to cultivate an identification with history by embracing the civil-rights movement, though this is hardly a controversial stance at a time when Martin Luther King Jr.’s birthday is a national holiday and even Glenn Beck claims his legacy­. But even then, Obama embraced a sanitized version in which the movement represents a fulfillment of basic American ideals, not the unfulfilled “revolution of values” that King hoped to see. Obama doesn’t invoke the radical King who spoke of “democratic socialism,” launched the Poor People’s Campaign, and supported the antiwar movement.

Another historical figure that Obama has consciously channeled is Abraham Lincoln. He announced his candidacy in 2007 in Springfield, Illinois, Lincoln’s hometown, and took the oath of office on the same Bible that Lincoln used for his inauguration. But unlike Lincoln, who respected people to his left such as the abolitionist Frederick Douglass and the Radical Republican leader Charles Sumner and took their objections to some of his policies seriously, Obama seems to view criticism as little more than an annoyance. He has accused liberal critics of being sanctimonious purists, more interested in staking out a principled position than in getting things done. Lincoln welcomed criticism; Obama, who has always considered himself (and often has been) “the smartest guy in the room,” doesn’t appear to think that he has much to learn from others. Alternative viewpoints never seemed to penetrate his administration’s inner sanctum.

“The American Radical Tradition” was never a simple course to teach. It presumed a basic knowledge of “mainstream” American history that not every undergraduate has, and it attracted an unusually diverse group of students, from history majors looking to complete departmental requirements to activists in search of a usable past. Many students, nonetheless, seemed to enjoy learning a history that few had encountered before. The online evaluations asked students to record what they took away from the course. “This class gave me a totally new perspective on American history,” said one. “The course taught me how to approach American history with a critical lens,” said another. And a third, perhaps a bit overenthusiastically, proclaimed: “I learned how to start a revolution.”

I taught a version of this course every three to four years since the mid-1970s. Given the conservative climate that has gripped our politics and the marginalization felt by many activist students, I’ve usually concluded it by warning against discouragement and reminding the class that every generation of Americans has witnessed some kind of radical upsurge. Despite overwhelming odds, I pointed out, Douglass, Debs, King, Elizabeth Cady Stanton, Margaret Sanger, Malcolm X, and the many others we studied did not give up hope: They were willing to fight and lose for a long time before achieving even partial success. And it’s also important to remember that all revolutions are unfinished, all triumphs incomplete, and every success or failure simply sets up the next series of struggles.

This past spring, those warnings proved unnecessary. I was afraid that disappointment with Washington gridlock and the modest parameters of change during the Obama years would have left my students disillusioned with politics. I needn’t have worried: Whatever their thoughts about Obama, so many of them were energized by the Sanders insurgency that 2016 turned out to be a propitious moment for teaching the history of radicalism. Like many upsurges of radicalism in the past, Bernie’s came as a complete surprise. Not long ago, the historian Steve Fraser published The Age of Acquiescence, which compared the first Gilded Age with our own and grimly concluded that unlike in the late 19th century, popular resistance doesn’t exist today. Fraser recently acknowledged that he’ll have to rethink that conclusion, because one of the achievements of the Sanders campaign was to crack open the lingering constraints of Cold War ideology and make economic inequality a part of the public discourse. More than a century ago, the German sociologist Werner Sombart famously asked, “Why is there no socialism in America?” The question these days is rather: “Why did so many voters support a self-proclaimed democratic socialist for president?” One poll found that among people ages 18 to 24, a higher percentage had a favorable opinion of socialism than of capitalism—a result that shouldn’t be surprising in view of the acute dysfunctionality of actually existing capitalism.

Whether the enthusiasm generated by the Sanders campaign will survive the recent election is difficult to say. But it requires a historical perspective to understand its roots and possibilities. Although in some ways a complete surprise, Sanders’s challenge did not spring from the void: Its emergence was foretold by the Seattle demonstrations against the World Trade Organization in 1999 and, more recently, by Occupy Wall Street and similar protests around the country; the movement for a $15 minimum wage; the remarkable success of Thomas Piketty’s Capital in the Twenty-First Century; and the movements against the deportation of immigrants, mass incarceration, and police mistreatment of people of color. As it unfolded, Bernie’s campaign offered me numerous opportunities to link the past and the present. The day The New York Times endorsed Hillary Clinton for the Democratic nomination on the grounds that Sanders wasn’t pragmatic enough, my students discussed the antislavery movement. “What exactly constitutes political practicality?” I asked them. For much of the 1850s and the first two years of the Civil War, Lincoln—widely considered the model of a pragmatic politician—advocated a plan to end slavery that involved gradual emancipation, monetary compensation for slave owners, and setting up colonies of freed blacks outside the United States. This harebrained scheme had no possibility of enactment. It was the abolitionists, still viewed by some historians as irresponsible fanatics, who put forward the program—an immediate and uncompensated end to slavery, with black people becoming US citizens—that came to pass (with Lincoln’s eventual help, of course).

Each time I taught “The American Radical Tradition,” I concluded by predicting (with greater confidence at some times than others) the emergence of a new generation of American radicals. I reminded my students that radicalism has always been hard work. There is truth in Oscar Wilde’s witticism “The problem with socialism is that it takes up too many evenings.” But today, we live in a moment of opportunity. As Antonio Gramsci observed at the end of World War I, the old order is dying, but the new one cannot yet be born. For a while after the end of the Cold War, it seemed like we were condemned to live in a world where the only alternatives to unregulated capitalism were religious fundamentalism or xenophobia and racism. Then the financial collapse of 2008 drove a stake through the heart of neoliberalism, the dominant ideology of the past generation (although its ghost still walks the earth, including the corridors of the Obama administration). The great achievement of the Sanders campaign was to step into the vacuum and begin to offer a new vision. The election of Donald Trump, while disastrous in so many ways, is yet another illustration of the bankruptcy of neoliberalism. It is also an opportunity for the left to forge a new set of policies to promote political, social, and economic equality.

Any new radicalism needs to learn from the past, but not simply to reenact it. The new American radicalism must be open and multifaceted, speaking the language of American society but receptive to insights from an increasingly interconnected world. One thing I think we’ve learned is that pinning one’s hopes on a single individual (including Obama and Sanders) is a recipe for disappointment. Maintaining the energy of popular mobilizations takes precedence over devotion to any individual. Nor is there a need for a single “party line”: Abolitionists and feminists both divided into a host of small groups. Following different, even contradictory paths may well produce greater strength rather than fragmentation and weakness. At the same time, single-focus organizations, which have proliferated in the last generation, need to recapture the sense of being part of a larger movement for social change that addresses diverse groups and interests—something that the Socialist Party before World War I went at least part of the way toward embodying.

On the first page of the course syllabus, I always included the words of Max Weber, a rebuke to those who believe that critics of society should set their sights only on “practical” measures: “What is possible would never have been achieved if, in this world, people had not repeatedly reached for the impossible.”