In the shadow of Trump Tower, protesters carried signs that read, “Gay Rights are Human Rights” and “This is the Best Protest, No Protest Has Ever Been Better,” (a sarcastic reversal of Trump’s signature superlatives). From among the throng, a young Asian woman, no more than 24 years old, no taller than 5 feet, pushes by me to photograph the protest. As she lifts her camera, the crowd roars with applause as if a celebrity just entered the barricaded area. A chant then begins: “I reject the president-elect.” After a few minutes, there is a lull. The young woman stops adjusting the lens on her camera and then, in a diffident voice that is barely audible, offers her own protest cry: “Climate change is real.” In the midst of catchy slogans and compelling chants, her somewhat tangential (if accurate) statement begins to be heard. She repeats it a few more times, though never raising her voice more than a decibel. Others begin screaming it. Within seconds, it can be heard down Fifth Avenue.

This is why protest matters.

Some Republicans have criticized the recent protests against Donald Trump’s election as rallies for crybabies. But they’re wrong. Protests have the stunning, almost magical ability to allow everyone’s voice to be heard.

While that may sound Pollyanna-ish, I can assure you, as someone who has spent my entire career teaching the history of protests, this is true. Protests have throughout history given people a voice even when they did not have the vote. In an era before suffrage, antebellum women in the North joined the abolitionist movement and gained prominence voicing their concern against an economic system that subordinated them. They spoke up in crowded lyceums, often the province of male speakers, and condemned the institution of slavery. They circulated petitions among their neighbors and then sent them to politicians in Washington, D.C. They stood up from their pews in church and told their congregations about the violence committed against enslaved people in the South. During the same time, in the mid-19th century, freed slaves with no more than the clothes on their backs organized one of the most profound political campaigns in world history. Born into slavery, with no political capital, they convinced the Republican Party to become their advocates and to join them in their fight for citizenship and suffrage. By voicing their political visions, first to each other and then to government officials who were stationed in the Reconstruction South, their voices eventually reached Washington, D.C., spurring the drafting of the Fourteenth and Fifteenth Amendments.

The Trump protests helpfully reveal the anatomy and power of coalition protest movements, particularly in how they amplify the political concerns of many other groups that, previously, were largely working on their own campaigns. At one point during Saturday’s protest in New York, white protestors began screaming “Black Lives Matter.” A few moments later, the men in the crowd began chanting, “Her body, her rights,” and the women responded, “My body, my rights.” Then someone began screaming, “Trans rights are human rights.” Within the span of no more than 20 minutes, the crowd articulated a call for antiracism, a safeguard to protect women’s reproductive rights, and the political recognition of transgender people.

The Left has often been accused of representing too many factions and of not speaking with a singular voice—unlike the conservatives, who in the last few decades developed their own slogans, “Family Values,” and “Make America Great Again,” that fused nostalgia with political action.

Yet, leftist protests have created vital spaces to articulate the many assaults on American freedom. Speaking truth to power, as the popular activist adage suggests—even among a crowd of allies—matters. It provides solidarity and a collective framework necessary for the advancement of political goals. Few social movements in history have succeeded without such support. The abolition of slavery emerged among a constellation of reform efforts that spanned from the temperance movement to the free produce movement to early forms of women’s rights and labor activism. A century later, in the 1970s, the gay liberation movement in the United States unfolded alongside of the black civil rights movement and the rise of feminism.

In order for the quietest, most unassuming voice to be heard, an audience must be available to receive it. It’s a lot like the famous philosophical question, “If a tree falls in a forest and no one is around to hear it, does it make a sound?” Just as someone needs to be standing in the forest to hear the thump of the tree hitting the ground, we need to protest to hear each other.

The protest against Donald Trump’s election is only part of a larger struggle that has been unfolding for decades. Black, gay, environmental, feminist, and transgender activists have been each waging their own campaigns but have often been, by both design and practice, separated from each other. Yet the organizations of protest against Trump have locked these activists arm-in-arm. This is not to romanticize these protests nor to overlook the tensions among some of these groups; but the fact remains that the American Radical Tradition succeeds when there is collective rallying.

As I was leaving the protest on Saturday evening, I noticed a woman standing alone. She walked with a cane, and she had traveled from a town in Pennsylvania that she referred to as “Trump Country.” She said her husband had been accosted by an anti-Semitic cab driver a few days after the election. He told her not to call the police or to report him to the cab company. She agreed that she wouldn’t. Then, the following day, she got in her car and drove to the protests in New York City, where she told me—and the rest of Fifth Avenue.