The Women's March came to Washington, D.C., on January 21, 2017, the day after Donald Trump's inauguration. Its purpose was to call attention to the incoming president's history of appalling behavior toward women—behavior to which Trump had all but admitted in the infamous hot-mic moment during an Access Hollywood taping. "When you're a star, they let you do it," Trump had said. "You can do anything. Grab 'em by the pussy."

This was a statement that rightly offended millions of Americans of all political stripes—Trump's electoral fortunes were never lower than immediately after the tape's release—and thus the march held the promise of uniting the country around a universal, positive message: It's not OK to abuse women.

More than half a million people descended on D.C. for the march, making it the largest protest in the United States since the Vietnam War era. It was a fairly awe-inspiring spectacle. Walking just a few blocks from my apartment, I was greeted by a sea of pink hats. Many of the protesters had chosen to reclaim Trump's own vulgar language, and I saw dozens of signs bearing some variant of the slogan "This pussy grabs back." Others were less confrontational: A young woman with pink streaks in her brown hair held a sign that said, "To love, we must survive; to survive, we must fight; to fight, we must love." Her friend stood next to her, waving a sign that featured a hand-drawn Donald Trump with the universally recognized emoji for excrement atop his head and the words Dump Trump.

All in all, the Women's March was a success for the nascent anti-Trump movement informally known as the #Resistance. More people showed up to protest than to attend the inauguration—something that seemed to infuriate the president, forcing several Trump staffers to make false statements about the relative sizes of the crowds. (This was the genesis of presidential adviser Kellyanne Conway's now infamous line about "alternative facts.")

Yet many of the young leftists I interviewed told me they thought the protest was a disgrace. According to them, it became too inclusive.

"That's actually fucking right," said Laila, a 26-year-old Muslim woman and political activist, when I asked if that was why she did not attend the march. Although she lives in Washington, D.C., Laila skipped town that weekend. "I'm tired of being a poster child for someone else's attempt at inclusivity," she explained.

In her view, by including so many different perspectives, organizers had watered down the message and ended up marginalizing the people who should have been the focus. They took "an approach that co-opted the narratives of many who have already been fighting in this space, specifically, black women."

Laila was hardly the only young activist who felt that way about the Women's March. Juniper, a 19-year-old trans woman, castigated the event as "super white" and "super cisgender-centric." (Cisgender, the opposite of transgender, describes people who identify as the gender they were assigned at birth.) She was skeptical of it at best, she said. And others were even harsher.

"I hated it," said Ma'at, a student of color at American University. "It was super cis-centric. It was exclusive of trans identities. It was whitewashed. It just in general was very co-opting and ineffective."

"I just felt like it wasn't very sincere," said Yanet, a student of color at the University of Maryland. "It just felt like a moment for people who aren't as involved or didn't care before to feel like, 'Oh, I did something.'"

"Insincere" and "ineffective" will strike many readers as surprising ways for leftist activists to describe the most well-attended mass march in four decades. But it makes perfect sense when one considers the priorities of the new activist culture, which prefers quality—intellectual purity—over quantity. A protest is successful only if it highlights the correct issues, includes the right people—people who check all the appropriate boxes—and is organized by a ruling coalition of the most oppressed. This is what intersectionality dictates.

Though the words intersectionality and inclusion sound like synonyms, they are actually in conflict with each other—a conflict perfectly encapsulated by the Women's March and activists' dissatisfaction with it. In case there was any confusion, Roxane Gay, a celebrated feminist author and voice of the left, tweeted this in response to the idea of people who oppose abortion participating in the event: "Intersectional feminism does not include a pro-life agenda. That's not how it works!"

Intersectionality is the operating system for the modern left. Understanding what it means and where it comes from is essential for comprehending the current state of activism on college campuses, at protests in major cities, and elsewhere.

Put simply, the idea is that various kinds of oppression—racism, sexism, homophobia, transphobia, economic inequality, and others—are simultaneously distinct from each other and inherently linked. They are distinct in the sense that they stack: A black woman suffers from two kinds of oppression (racism and sexism), whereas a white woman suffers from just one (sexism). But they are also interrelated, in that they are all forms of oppression that should be opposed with equal fervor. For instance, a feminist who isn't sufficiently worked up about the rights of the gay community is at odds with the tenets of intersectionality. She is a feminist, but she is not an intersectional feminist.

Holly, a 23-year-old Berkeley student whom I met at the April 2017 People's Climate March in Washington, D.C., told me that for her, intersectionality means all issues are "connected and tie in with each other, like indigenous rights, Black Lives Matter, and climate change."

Kimberlé Williams Crenshaw, a law professor at the University of California, Los Angeles and Columbia University, coined the term intersectionality in her 1989 paper "Demarginalizing the Intersection of Race and Sex." She needed a word to describe the lives of black women who were discriminated against because of both their race and their sex. Their experiences were fundamentally different from those of black men, who were privileged to the extent that they were men, and from those of white women, who were privileged to the extent that they were white.

"Discrimination, like traffic through an intersection, may flow in one direction, and it may flow in another," wrote Crenshaw. "If an accident happens in an intersection, it can be caused by cars traveling from any number of directions and, sometimes, from all of them. Similarly, if a Black woman is harmed because she is in the intersection, her injury could result from sex discrimination or race discrimination."

Crenshaw got the idea from a 1976 federal district court case, DeGraffenreid v. General Motors, in which five black women had sued the auto giant. They argued that G.M.'s policy of laying off the most recently hired employees violated Title VII of the 1964 Civil Rights Act, which prohibits both racial and gender-based discrimination. Since it had been only a little more than a decade since the law had begun requiring G.M. to hire black and female employees, the most recent hires tended to be black women, the plaintiffs argued.

But the court determined that black women enjoyed no special protection under the law—the employees were protected from racial discrimination and gender-based discrimination, but not from the combined effects of these two categories. "The plaintiffs are clearly entitled to a remedy if they have been discriminated against," wrote the court. "However, they should not be allowed to combine statutory remedies to create a new 'super-remedy' which would give them relief beyond what the drafters of the relevant statutes intended."

DeGraffenreid v. General Motors was Crenshaw's lightbulb moment. Black women lived in the midst of two kinds of discrimination—racism and sexism—and thus languished under an oppressive force greater than the sum of its parts.

"What Kimberlé is saying with intersectionality is that, in order to understand how power operates, you have to understand how people live their lives," says Alicia Garza, an activist and co-founder of the Black Lives Matter movement. "Intersectionality is the very basic notion that we live multiple experiences at once. It's not just, 'Oh, I'm black and I'm a woman and I'm a black woman.' It's to say that I'm uniquely discriminated against. I uniquely experience oppression based on standing at the intersection of race and gender."

Though Crenshaw came up with the term, the concept itself predates her. As far back as 1892, the black feminist Anna Julia Cooper had criticized leading anti-racists for failing to advance the cause of black women. "Only the black woman can say when and where I enter, in the quiet undisputed dignity of my womanhood.…Then and there the whole race enters with me," she wrote in A Voice From the South.

For the Boston-based black feminist lesbian organization known as the Combahee River Collective, which existed in the 1970s and early '80s, "simultaneity" was the word used to describe the cumulative impact of the various oppressions they experienced. Their manifesto called not just for the abolition of racism and sexism but for "the destruction of the political-economic systems of capitalism and imperialism as well." Avowed enmity toward all the various -isms: This is the strategy required by the intellectual framework that became known as intersectionality.

Patricia Hill Collins, a professor of sociology at the University of Maryland, expanded upon Crenshaw's work, publishing Black Feminist Thought: Knowledge, Consciousness, and the Politics of Empowerment in 1990. Taking a cue from Crenshaw, she used the term intersectionality to refer to the interlocking matrices of oppression that serve to marginalize people. Initially focused on race and gender, Collins gave additional consideration to class as a matrix in her 1992 book Race, Class and Gender: An Anthology. Later, she would add sexual orientation to the mix. "Intersectional paradigms view race, class, gender, sexuality, ethnicity, and age, among others, as mutually constructing systems of power," she wrote in 2004's Black Sexual Politics. "Because these systems permeate all social relations, untangling their effects in any given situation or for any given population remains difficult."

That's quite the understatement, since every new addition to the list of interrelated oppressions makes the task even more cumbersome. There are more of these categories than most people might imagine, and every year, intellectual peers of Crenshaw and Collins propose new ones. Meanwhile, intersectionality has become a ubiquitous force on college campuses, where young people are taught to perceive all social issues through the lens of interrelated oppression and to find more grievances to add to the pile. Those who grasp the truth of intersectionality are said to be "woke," slang that describes someone who has awakened to the reality of their own privilege and adopted a progressive worldview.

The spread of intersectionality poses some problems for the left, since the theory divides people as often as it unites them. In recent years, Hulu's The Handmaid's Tale, a prestige drama based on feminist author Margaret Atwood's beloved novel, became mandatory #Resistance viewing for its depiction of an oppressive society where women have been enslaved by theocratic authoritarians—a future toward which Trump's America is hurtling, according to many on the left. But the second season, which debuted in 2018, drew criticism: The show was accused of a "failure of intersectionality" because it never grappled with racism, only sexism. "This is a show all about gender—it is built entirely around that concept—but until The Handmaid's Tale learns to make its feminism intersectional, it's going to keep letting its audience down," commented BuzzFeed TV writer Louis Peitzman.

In the years since Crenshaw introduced the term, intersectionality has broadened in both scope (that is, more kinds of oppression have been identified) and reach (more people are aware of the concept and what it implies).

The academy loves intersectionality, and the theory's popularity has soared in sociology, psychology, English, philosophy, history, and other social science and humanities departments. Indeed, more and more universities have created entire academic wings dedicated to studying specific kinds of oppression and explaining how they relate to others. Thus the rise of women's studies, African American studies, Hispanic studies, Asian studies, queer studies, and more.

What began at the intersection of race and sex now includes economic class, gender identity (the gender category to which a person feels attachment, which may be different from the person's biological sex), gender expression (the way a person looks and behaves), sexual orientation, immigration status, disability status, age, religious belief (though certain believers—such as Muslims—are perceived as more oppressed than others), and size (whether you are overweight or not).

In practice, intersectionality frequently forces the left to engage in self-cannibalism. Not all victims of oppression get along, since they're quite often in tension with each other. The intersectional progressive says, in effect: "We must fight racism, and sexism, and homophobia, and transphobia, and the Trump administration's immigration policies, and the wealthy, and global warming, and anti-Muslim bigotry, and ableism, etc." There are millions of people, though, who want to fight some of these things but not others—and if intersectionality requires them to commit to every single cause at once, they simply won't.

Some people might decry racism and sexism without fully understanding or agreeing with the demands of the trans community; indeed, there's a community of feminists who specifically reject the notion that trans women should be considered women. Other people might want economic equality for the poor but hold socially conservative views on gay rights, or oppose Trump's harsh treatment of immigrants but feel ambivalent about climate change. Still others might be strident progressives in nearly all respects but dissent from the notion that Muslims deserve space in the club when Jews do not.

That's not a theoretical example. In modern progressive parlance, Muslims are oppressed and Israel is the oppressor. Thus, anti-Islamic bias is viewed as a source of oppression, while anti-Semitism is frequently ignored—even though Jews tend to be much more politically progressive than Muslims.

There are three main problems with intersectionality: the education problem, the perfection problem, and the coalition problem.

First, the problem of education. One important implication of intersectionality is that the sole authority on an individual's oppression is the individual in question. White men who are heterosexual and cisgender shouldn't try to "mansplain" the struggles of black women or people of color: They aren't oppressed, so they can never understand what it's like, even if they happen to be extremely progressive or well-educated about left-wing causes.

At the same time, "it's not my job to educate you" is one of the most frequently recited catchphrases in activist circles. "It is not my responsibility as a marginalized individual to educate you about my experience," wrote Elan Morgan in a popular Medium post, which provided 21 arguments for why that statement was correct. The feminist news website Everyday Feminism has highlighted the work of YouTuber and transgender activist Kat Blaque, who opined in a video that it is "demeaning and dehumanizing to explain to people of privilege why people like them have historically and currently oppressed people like me." And in an article for HuffPost, the feminist writer Melanie Hamlett wrote: "Dear Men, It Is Not My Responsibility to Explain Feminism to You." Doing so, she said, required too much "emotional labor."

But here we have an obvious issue: Asking people about their oppression—even earnestly, out of a sincere desire to become better educated—is discouraged, and there's no other way to gain this knowledge, since the oppressed themselves are the only acceptable experts. This makes it frustratingly difficult to have supportive conversations about oppression, let alone tense ones.

The second problem, which follows logically from the first, is the perfection problem. Very few people can grasp with 100 percent accuracy the various requirements of intersectional progressivism, given that they aren't allowed to interrogate the oppressed, who are the only source of knowledge about their oppression. I once saw this issue explained perfectly in a blog post, written by a woman complaining about all that was required of her. "As an ally, my job is to not impose my own beliefs of what's 'right,' but instead amplify the voices of the oppressed people that I'm trying to be an ally for," she wrote. "Except that I shouldn't bug them about educating me, because that's not what they're there for. And it's my duty to talk about the issue of oppression in question, because it's the job of all of us, rather than the oppressed people, to fix it. Except that when I talk, I shouldn't be using my privilege to drown out the voices of the oppressed people. Also, I should get everything right, 100% of the time. Including the terminology that the oppressed people in question themselves disagree on."

Even the most well-intentioned person is bound to slip up. My Facebook feed recently served up a note from someone asking for help finding shelter for a wheelchair-bound neighbor. The immediate reply was this: "The only resource I have for you at the moment is in regards to the words wheelchair bound," accompanied by a link to a HuffPost article titled "Stop Saying 'Wheelchair-Bound' and Other Offensive Terms." You probably didn't know wheelchair-bound was offensive terminology—I certainly didn't—and in any case, you shouldn't ask someone in a wheelchair what the correct terminology is, because it's not that person's job to educate you.

In The Daily Beast, Kristen Lopez described the 2018 Marvel superhero film Ant-Man and the Wasp as "ableist"—that is, disparaging of people with disabilities—for including a character who suffers from chronic pain and is attempting to cure her condition. "Instead of helping Ava find a way to cope [with] (and not necessarily eradicate) her disability, the film seeks to provide a cure." That's a bad thing, Lopez wrote, because not all disabled people want to overcome their disability. Who knew you could run afoul of disability activism by making a movie in which a character who suffers from chronic pain tries to overcome it?

The writer, academic, and activist Fredrik deBoer once described an event he witnessed: "A 33-year-old Hispanic man, an Iraq war veteran who had served three tours and had become an outspoken critic of our presence there, [was] lectured about patriarchy by an affluent 22-year-old white liberal arts college student." The veteran had committed a crime of the "wheelchair-bound" variety: He had called on other veterans to "man up" and denounce the war. What he could not have known, since he had spent much of his adult life on a battlefield rather than in feminist studies lectures, is that man up is a gendered term and thus unacceptable.

According to deBoer, these incidents frequently result in would-be allies growing disheartened with the cause. Nobody's perfect—and that's an issue for intersectionality, since it demands total adherence to all facets of its approach.

The third problem, which grows out of the first two, is the coalition problem: The demands of intersectionality make it extremely difficult to form strategic relationships for the purpose of advancing a single issue.

Take legalizing marijuana, for example. There are a lot of Americans who subscribe to a diverse range of ideologies with some interest in the issue. There are liberals and leftists who think using marijuana is no big deal, there are libertarians who think the government has no right to tell consenting adults what they can put in their own bodies, and there are even some conservatives who think enforcing federal marijuana prohibition is a waste of law enforcement resources and a blow to states' rights. People from all three of these groups could and should work together to advance the cause, despite their myriad differences on other issues. But intersectionality gets in the way, since the intersectional progressive only wants to work with people who oppose all the various strains of oppression—not just the ones relevant to the narrow issue of marijuana policy.

It's difficult to imagine that the campaign for gay marriage would have gone as relatively smoothly as it did had intersectionality been as ubiquitous a decade ago as it is today. This was in some sense the last nonintersectional leftist cause: Activists who supported it were extremely disciplined and specifically avoided tying it to other, more fringe issues. Believers in same-sex marriage, in fact, worked tirelessly to bring people on the political right into the movement, stressing that gay couples only wanted legal equality and sought to form the same kinds of family arrangements that social conservatives believe are desirable for society. The marriage equality movement even turned to Ted Olson, a Republican and former solicitor general under President George W. Bush, to represent it in the lawsuit against California's Proposition 8, which had banned gay marriage in the state.

One of the strongest voices on this issue was Andrew Sullivan, a gay right-of-center writer who made the case for same-sex marriage in a 1989 New Republic article: "Marriage provides an anchor, if an arbitrary and weak one, in the chaos of sex and relationships to which we are all prone," he wrote. "It provides a mechanism for emotional stability, economic security, and the healthy rearing of the next generation. We rig the law in its favor not because we disparage all forms of relationship other than the nuclear family, but because we recognize that not to promote marriage would be to ask too much of human virtue. In the context of the weakened family's effect upon the poor, it might also invite social disintegration."

That's a fundamentally conservative argument, crafted specifically to appeal to people on the right. And it worked. Support for gay marriage increased from 27 percent in 1996 to 67 percent two decades later. It is now legal everywhere in the United States.

This happy development is in large part due to the work of a coalition that would be impossible to put together in the age of intersectionality. Sullivan and Olson would almost certainly have been chased away by activists refusing to engage with them due to their conservative views on other policy matters.

Contrast the triumph of gay marriage with some examples of the setbacks and infighting that occur within an intersectional framework. During the June 2017 Chicago Pride Parade, organizers asked Laurel Grauer, a Jewish lesbian, to leave. Grauer had dared to carry a flag bearing a rainbow (the symbol of the LGBT community) and the Star of David. She was told her display made people feel unsafe. One might expect everybody who supports equal rights and dignity for LGBT people to be welcome at pride events, but from the standpoint of the organizers, the march was intended to be intersectional—meaning it was both pro-LGBT and "anti-Zionist," or opposed to the state of Israel's existence.

For the modern left, Jews are outranked by minority groups whose oppression is considered more serious than, and to some degree at odds with, their own. The incident at the Chicago Pride Parade is not a one-off. Linda Sarsour, an activist and Women's March leader, has made the dubious claim that anti-Semitism is "different than anti-black racism or Islamophobia because it's not systemic."

Sarsour and fellow Women's March leaders Tamika Mallory and Carmen Perez have drawn criticism for their ties to controversial Nation of Islam leader Louis Farrakhan, who is widely considered to be anti-Semitic. Farrakhan has compared Jewish people to termites and asserted that "powerful Jews are my enemy." He made the latter remark at a February 2018 rally attended by Mallory, who distanced herself from his rhetoric but would not condemn the man himself—and who was steadfast in her commitment to working with his group.

Or consider an illuminating episode involving the Democratic Socialists of America (DSA), a left-wing group that got a huge boost from Bernie Sanders' 2016 presidential campaign. In January 2018, the DSA tweeted that it would be unveiling its Medicare for All campaign, an effort to extend the national health insurance program to everyone in the country.

This was an unsurprising development—empowering the government to provide more comprehensive health care coverage is a fairly standard goal of liberal activists, not just the far left. More surprising was the furious blowback the DSA received from many of its own members who identified as disabled. The DSA's Medicare for All committee had apparently failed to consult the Disability Working Group about the campaign's rollout, which led the latter to protest that they were being excluded from relevant decision making. Since disabled people are especially affected by health care policy, the Medicare for All group had essentially failed to let disabled people be the experts on their own oppression—an intersectionality no-no.

Amber A'Lee Frost, a Medicare for All proponent and prominent DSA member known for co-hosting the left-wing Chapo Trap House podcast, hit back, accusing her critics of trying to sabotage the movement with their "pathological anti-social behavior." This made matters much worse: The comment was perceived as an attack on the autistic community.

Frost had committed ableism. Several dozen DSA members signed a petition demanding that she "immediately remove herself from any involvement, official or unofficial, with DSA's Medicare for All campaign, and should she not, that she be removed." This was necessary, because intersectionality means casting suspicion on organizing efforts if these efforts do not make the marginalized the center of attention.

College campuses, where the grievances are significant but the stakes are low, play host to some of the most farcical examples of intersectionality-induced bickering. A particularly revelatory crisis emerged at Evergreen State College in Washington during the spring 2017 semester.

Every year, activists there organized a Day of Action during which students of color would deliberately leave campus as a means of protest against racism. But in 2017, the activists decided to try something new: They would ask students of color to remain and white people to leave.

This tactic didn't sit well with Bret Weinstein, a biology professor at Evergreen. Weinstein was a progressive—he had supported Sanders over Hillary Clinton the year before—and sympathized with the activists' goals, but he felt that the new plan for the Day of Action was unsound. "There is a huge difference between a group or coalition deciding to voluntarily absent themselves from a shared space in order to highlight their vital and under-appreciated roles, and a group or coalition encouraging another group to go away," Weinstein told an administrator. The latter, he contended, "is a show of force, and an act of oppression in and of itself."

In response, activists surrounded Weinstein outside his classroom and accused him of being a racist. "This is not a discussion!" they told him. A student named Hadley later told Vice correspondent Michael Moynihan that her message to Weinstein was: "You don't get to spread this problematic rhetoric."

A subsequent dialogue between the activist students and college President George Bridges similarly spiraled out of control. During the meeting, activist students repeatedly belittled Bridges, a meek, bow-tie-wearing white man, even instructing him to keep his hands at his sides and stop pointing at people. "Fuck you, George!" one student said. "We don't want to hear a goddamn thing you have to say." When Bridges asked the students to let him leave the room so he could use the lavatory, they told him to hold it.

Hadley would tell Moynihan that Weinstein should go be a "racist and a piece of shit" somewhere else. The campus police said they could no longer guarantee the professor's safety on campus, and he eventually resigned.

Each of these examples shows how activists who worship at the altar of intersectionality felt compelled to turn on people for committing venial sins. It's not enough to share the intersectional progressives' goals relating to a specific issue: One must also support their tactics, know their language intuitively, defer to the wisdom of the oppressed without either speaking on their behalf or expecting them to speak for themselves, and commit to every other interrelated cause.

The intersectional approach often seems petty and performative. The symbol of the gay rights movement, the rainbow flag, was designed by activist Gilbert Baker in 1978. Its colors were pink, red, orange, yellow, green, turquoise, indigo, and violet, which he said represented sex, life, healing, sunlight, nature, magic, serenity, and spirit. In 2017, Philadelphia debuted a new rainbow flag to celebrate Pride Month—this one including brown and black stripes, in recognition of people of color.

Many members of the LGBT community—particularly younger ones, according to BuzzFeed—liked the new intersectional flag, which takes a stand against homophobia and racism. But many older LGBT activists were confused, since none of the original colors reflected ethnicity at all. Will the flag eventually have to add stripes for Latinos, Asians, and Native Americans? What about the disabled community and those who languish under the oppression of sizeism?

The thinkers who first defined intersectionality probably hoped that by linking all kinds of oppression together, they could force people to fight against a wider swath of bad things. The University of Maryland's Collins hinted at this when she wrote that "many African Americans deny the existence of sexism, or see it as a secondary concern that is best addressed when the more pressing problem of racism has been solved. But if racism and sexism are deeply intertwined, racism can never be solved without seeing and challenging sexism." Collins wanted to tie the problems together so that everybody fighting one would have to fight the other, too.

But the more -isms added to the pile, the more tenuous this approach becomes. It's all well and good to say that sexism is as pervasive a problem as racism, but the intersectional activist of 2019 is reaching much further and making many more demands. From the standpoint of this movement, a woman marching against the Republican Party, against police brutality, against war, against sexual violence, and for Israel's existence is not an ally or potential ally: She is an enemy. She is part of the problem. She has failed the test of intersectionality. She is not, as the poet Elisa Chavez put it, "intersectional as fuck." She might as well have voted for Trump.

A hopelessly divided opposition movement that cannot resist cannibalizing itself over intersectionality-induced disagreements is not going to be very effective. In fact, it's probably a good recipe for the continued political dominance of the Trump coalition.

Adapted from Robby Soave's new book, Panic Attack: Young Radicals in the Age of Trump, by permission of All Points Books/St. Martin's Press.