How Black is Kamala Harris? That the question gets posed speaks to the ill-defined contours of an ill-defined concept. Ms. Harris, the daughter of an Indian-born mother and a Jamaican-born father, has been called in the media “half Black,” “biracial,” “mixed race” and “Blasian.” In online posts, people have ventured that she’s “partly Black” or — for having attended Howard University, a historically Black school — an “honorary full Black.” Others persist in asking whether she’s “Black enough.”

The old British concept of “political Blackness,” the heyday of which stretched from the late 1970s to the early 1990s, would make nonsense of such questions in a very immediate way: Ms. Harris’s mother, by this definition, is just as Black as her father. For proponents of political Blackness, “Black” was an umbrella term that encompassed minorities with family origins in Asia and the Middle East as well as in Africa and its diaspora. That’s not to say it was the sturdiest of umbrellas: It was never uncontested. Yet it may have lessons for us today.

In Britain, anyway, its legacy remains legible. Three years ago, in a public-awareness campaign designed to increase voter turnout among British minorities (“Operation Black Vote”), Riz Ahmed, a British actor and rapper of Pakistani parentage, appeared on a video. “Blacks don’t vote,” he said. “And by Black people, I mean ethnic minorities of all backgrounds.” The year before, the student union at the University of Kent attracted attention when it promoted Black History Month with the faces of six famous figures: Alongside four British people of African descent, it posted two of Pakistani heritage — the pop star Zayn Malik and Sadiq Khan, the mayor of London.

During its roughly two decades of prominence, the political Blackness movement, taking note of how Britishness had routinely been equated with whiteness, was especially devoted to the “Afro-Asian” alliance. (In Britain, the term “Asian” defaults to South Asian.) During the 1980s, the movement’s inclusive usage of “Black” went mainstream in Britain. The Commission for Racial Equality, a public body established in 1976, decided that “Asian” would be a subcategory of “Black”; other such organizations followed suit. The bien-pensant among the children of empire started styling themselves as Black, whether or not they had sub-Saharan ancestors.

Of course, this broadened sense of “Black” wasn’t exactly a novelty. Malcolm X, in a speech from 1964, heralded Black revolutionaries around the world and explained: “When I say Black, I mean nonwhite. Black, brown, red, or yellow.” Anyone who had been colonized or exploited by the Europeans qualified. And Malcolm X, in turn, was drawing on an internationalist tradition captured six decades earlier by W.E.B. Du Bois. “The problem of the 20th century,” he wrote, “is the problem of the color line; the relation of the darker to the lighter races of men in Asia and Africa, in America and the islands of the sea.”

In Britain, this capacious usage of “Black” scanted the enormous differences among the nation’s nonwhite minorities. But that was exactly its point, and its power. The great cultural theorist Stuart Hall — you could see this elegant figure on British television in those days, with his close-cropped beard and well-fitted blazers, lecturing for the Open University — was always warning against the way “race” presented itself as a natural fact about human beings. Using “Black” as an umbrella term, he felt, would weaken such illusions: It would helpfully emphasize the “immense diversity and differentiation of the historical and cultural experience of black subjects.”

In an influential 1988 essay on “black cultural politics,” for example, Mr. Hall celebrated a film by John Akomfrah, whose father (like mine) had been a Ghanaian politician. Yet he also cited the writer Hanif Kureishi’s two collaborations with the director Stephen Frears, “My Beautiful Laundrette” and “Sammy and Rosie Get Laid,” as significant contributions to Black cinema. That neither Mr. Kureishi nor Mr. Frears was of African descent didn’t make the work less Black.

Only such an inclusive conception of Blackness, proponents maintained, could effectively counter an exclusive conception of Britishness. Ambalavaner Sivanandan, a political thinker and the longtime director of the London-based Institute of Race Relations, saw strategic benefits in “the forging of black as a common color of colonial and racist exploitation.” As a young man in the late 1950s, Siva, as he was known to his friends, left behind the ethnic strife of Sri Lanka and went to London, only to witness attacks by white youth on West Indians in the Notting Hill neighborhood. “I knew then I was black,” he would write.

Opponents of political Blackness tended to suspect that Asians were being forced into a template set by Afro-Caribbeans. In the early 1990s, the sociologist Tariq Modood cited a survey that suggested only a third of British Asians identified as Black, and argued that Asians suffered more from racial prejudice in British society than people of African descent did. White working-class youth were drawn to Afro-Caribbean culture, he said, while turning against Asians. It galled him, too, to see anti-racist programs focused on Afro-Caribbeans when most non-white British people were Asian.

And there’s no doubt that the social reality on the street didn’t always harmonize with the high-minded aspirations to shared struggle. Claire Alexander, a sociologist at the University of Manchester, has dryly recalled that when she did fieldwork in the late 1980s about how Black British youth created their cultural identities, “one of my main informants, Darnell, commented, laughing, ‘you know, Claire, Blacks and Asians don’t get on.’”

Yet the various criticisms of political Blackness presented quandaries of their own. Sure, the umbrella concept didn’t give voice to all the differences it encompassed, but it wasn’t meant to supplant the many other sources of identity in people’s lives. Besides, a term like “Asian” itself ignored the immense internal diversity of the group it designated. Among British Asians, Sikhs and Hindus didn’t vote the way Muslims did. Islamophobia targeted Asians but was also promulgated by Asians.

Mr. Hall, warning against the fiction that “all black people are the same,” had no illusions that Afro-Caribbeans were a cohesive group, either. When he was growing up in Jamaica, he recalled, nobody was ever called “black,” but colorism — prejudice against those with a dark skin tone — was rampant: His grandmother could distinguish 15 hues of brown. Social groups, he knew, are fractal. By the logic of culture, creed, color or kinship, you could always split them into smaller groups. So why not lump them into larger ones, too?

In Britain today, the arguments for splitting and lumping — for specificity and commonality — remain unresolved. The Black Students’ Campaign, the largest organization of nonwhite students in Britain and Europe, represents students of Asian and Arab heritage as well as those of Caribbean and African descent. A few years ago, chastened by critics of the “Black” umbrella, the organization decided that it needed a new name and asked members for suggestions.

Those Black History Month posts at the University of Kent certainly came under fire for including people of Pakistani heritage. “Ill-thought and misdirected” was an institutional tweet from Black History Month UK. The Kent student union “unreservedly” apologized on its Facebook page. The offending faces were purged.

When Riz Ahmed appeared in the public service announcement for Operation Black Vote, some people were eager to see his face purged, too. The journalist Yomi Adegoke remarked, “When I’m followed around in an Afro-Caribbean hair shop or newsagent, an Asian vendor forgets all about political blackness and becomes far more occupied with blackness-blackness.”

But there have been voices for lumping, too. “As children in the 1980s,” Mr. Ahmed wrote somberly, “when my brother and I were stopped near our home by a skinhead who decided to put a knife to my brother’s throat, we were black.” Emma Dabiri, an author and broadcaster (“Irish-Nigerian” is how she designates herself), recently called for “the identification of affinities and points of shared interest beyond categories that were invented to divide us.” And, as it happens, the Black Students’ Campaign never found a replacement for “Black,” and the group still includes Arabs and Asians.

ImageA political demonstration in London in 1968. 
Credit…Henning Christoph/Ullstein Bild, via Getty Images

There’s a reason that “political Blackness” never gained much purchase in the United States. In Britain, what matters most is whether or not you’re white; in America, what matters most is whether or not you’re Black.

Still, in the United States today, similar debates roil over “people of color” and the acronym now in favor, BIPOC (for Black, Indigenous and people of color). Does such nomenclature suggest that all nonwhite people are interchangeable? Indian-Americans have a household income that’s two-thirds higher than the national median; for Black people, it’s a third lower. Should these groups share an umbrella? Does the language of generality blunt the sharp analysis of racial disparities we need?

Damon Young, the author of the memoir “What Doesn’t Kill You Makes You Blacker,” calls “people of color” a “valueless catchall that extinguishes identity instead of amplifying it.” Jason Parham, in Wired, has dismissed “people of color” as an “idiomatic casserole of cultures and identities.” If you mean Black people, say Black people, such critics argue. And they have a point.

The hitch is that the term “Black people,” too, is a casserole of cultures and identities. Anti-Black racism can be a useful concept. But it’s equally an umbrella, casting its shade over the fact that in socioeconomic terms, British Caribbean immigrants and their children and grandchildren in the United States have fared better than “native” African-Americans and that those from the French- and Spanish-speaking Caribbean have fared worse. It also obscures the fact that colorism, even within Black America, can entail another set of disparities in treatment.

And while some African-American critics think “people of color” is hopelessly expansive, others think the same of “African-American.” The political movement ADOS, which stands for American Descendants of Slavery, wants to establish what it considers a properly “cohesive” notion of Black identity, fencing out people like Barack Obama and Kamala Harris as “New Black” usurpers of a native lineage of suffering. (For some of those who take Blackness as a badge of dispossession, Ms. Harris’s father’s elite education makes him a suspect member of the Jamaican comprador bourgeoisie.) Every tribe, it’s clear, contains other tribes. It’s umbrellas all the way down.

Reflecting on political Blackness, then, should encourage us to retrain some of our reflexes. The identity group that we invoke should be “right-sized” to our needs and aims. Sometimes we’ll want to contract a category for purposes of analysis; sometimes we’ll have reason to expand a category for purposes of solidarity. Indeed, if the context is white nationalism and the anxieties of membership in an eroding demographic majority, “people of color” may be an invaluable analytic term. The salient distinction there is between white and nonwhite.

What about the ADOS movement? If ADOS activists flounder — they have fixed their gaze on slavery reparations and are intent that the wrong people don’t get in on the action — it will be because their certain-Black-lives-matter-more approach proves politically misjudged. An ambitious goal like reparations may require broad support, and in turn a broad conception of “Black.” Skeptics might think that, as with the prospectors and fortune hunters of “The Treasure of the Sierra Madre,” ADOS’s determination to keep the rewards for themselves imperils the chances of anyone getting them.

But let’s say you’re concerned about colorism. You might have been among those who were indignant when Zoe Saldana, a light-skinned Black woman, was cast in a biopic about Nina Simone, a dark-skinned Black woman. To talk about such prejudice, you’ll have to insist on one of the ways in which all Black people aren’t alike. You’ll have to split rather than lump.

Getting the identity aperture wrong — drawing a circle that’s too wide or too narrow, given our agenda — can lead to confusion or futility. When we’re told that about a third of Latinos support President Trump, should we wonder whether something has gone terribly wrong with Joe Biden’s ethnic outreach? Or should we wonder whether a demographic category that suggests a similarity of interests between Ted Cruz and Alexandria Ocasio-Cortez may — for these purposes, anyway — be eliding distinctions that matter more?

For these purposes is always the crucial qualifier. One’s purposes can involve coalition politics, cultural interpretation or socioeconomic precision. The point is that none of these identity terms is stenciled by the brute facts of the social world; rather, they stencil themselves upon the social world. Each is invariably a decision — a decision made jointly with others — that arises from our interests and objectives. You don’t like the available identity options? Start a movement; you may be able to change them.

By the cultural logic, or illogic, of race, Kamala Harris, like Barack Obama, counts both as biracial and as Black. Among major-party vice-presidential candidates, she qualifies as the first Asian-American, the first Indian-American, the first African-American, the first woman of color. Identities, of course, are multiple, interactive and, yes, subject to revision. As the architects of political Blackness rightly insisted, collective identities are always the subject of contestation and negotiation.

Political Blackness may have had its day, but we’re still coming to grips with its central insight: Blackness, like whiteness, has never not been political.

Kwame Anthony Appiah (@KAnthonyAppiah) is a professor of philosophy at New York University and the author, most recently, of “The Lies That Bind: Rethinking Identity.”

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