Sarah Lewis teaches art history and African American studies at Harvard.

In 1926, Sarah Lewis's grandfather, Shadrach Emmanuel Lee, was expelled from a Brooklyn public high school for asking why black people were not in his history textbook. His teacher told him African Americans had done nothing worthy of being included.

Last week, Lee's granddaughter and some of her friends - among them Ava DuVernay, Wynton Marsalis, Henry Louis Gates Jr., Carrie Mae Weems, Theaster Gates, Bryan Stevenson, Naomi Wadler and Yara Shahidi - had Harvard University in their thrall.

Lewis teaches art history and African American studies at Harvard. She was the driving force behind "Vision and Justice," a two-day convening focused on race and visibility. The event, which coincided with a career-spanning Gordon Parks exhibition at Harvard's Ethelbert Cooper Gallery (through July 19), will likely be remembered as a defining moment in the university's history.

The star-studded cast addressed everything from algorithmic bias and the Flint, Michigan, water crisis to the "adultification" of young African Americans and the human cost of mass incarceration. But the subject to which the speakers - who also included Chelsea Clinton, Teju Cole, Drew Gilpin Faust and David Adjaye - kept returning was visibility, and culture's role in promoting it. As Lewis herself said: "You can't fight the battle without pictures."

"Frederick Douglass knew it long ago," Lewis wrote recently: "Being seen accurately by the camera was a key to representational justice. He became the most photographed American man in the 19th century as a way to create a corrective image about race and American life."

There are pictures that are uplifting and inspiring, and others we may not want to see. Yara Shahidi and Naomi Wadler, two of the youngest speakers at "Vision and Justice," spoke poignantly about both kinds.

Shahidi is the 19-year-old star of the ABC sitcom "Black-ish" and its spinoff, "Grown-ish." Wadler is the 12-year-old student who led a walkout at her school over gun violence, then gave an unforgettable speech at the March for Our Lives protest. Wadler wanted us, she said in that speech, to see young African Americans killed by guns as "vibrant beautiful girls full of potential," rather than mere "numbers."

Shahidi, meanwhile, has a small tattoo that says simply, " '63." A number, yes, but it is also Shahidi's nod to the past. Specifically, her acknowledgment of the momentous things that happened in 1963, events that, half a century later, have helped make her visible: the March on Washington, Malcolm X's "Message to the Grass Roots" speech, the assassination of civil rights activist Medgar Evers and the publication of James Baldwin's "The Fire Next Time."

Shahidi, who credits her cousin, a rap artist, with introducing her to Baldwin's writing, quoted part of Baldwin's statement, from a famous debate with William Buckley, about the great shock, for an African American child, of discovering "that the flag to which you have pledged allegiance, along with everybody else, has not pledged allegiance to you."

The arts, Shahidi said, "have been a form of reclaiming my allegiance to a community that considers me."

What culture makes visible, in what way and by whom, were questions that came up repeatedly throughout "Vision and Justice." Wadler, for instance, recalled visiting the National Museum of African American History and Culture in Washington. "There are six floors of black history," she said, "and it was just so cool." Her history teacher (in contrast to Lewis's grandfather's teacher) had asked Wadler's class to think about both what they see and what they do not see.

So it was interesting to learn a version of that same question had plagued the museum's designer, Adjaye, as he was starting out in architecture. "I was alive, I was living," he said in a conversation with artist Theaster Gates, "but somehow I couldn't see the effects of my life in the world."

The son of a Ghanaian diplomat, Adjaye was born in Dar es Salaam in Tanzania and lived in Egypt, Yemen and Lebanon before moving to Britain at age 9. Where was the architecture, he wondered, that expressed today's realities of hyper-migration and the kind of explosion of hybridity seen in literature, art and other art forms? Why was contemporary architecture so inclined to "navel-gazing"?

Adjaye's design for the African American Museum (he worked with J. Max Bond Jr. and Philip Freelon) was an attempt at redressing the lack he perceived. Gates, in the course of complimenting Adjaye's work, spoke of his own visit to the museum. Like so many others, he found himself observing the hundreds of black students interacting with the exhibits. "You could see that they were their best selves, because they were proud of the image in front of them," he said.

Earlier in the day, Sarah Lewis had mentioned one of the most famous recent examples of a black child "seeing" himself - and, in a sense, being seen: former White House photographer Pete Souza's image of an African American boy, 5-year-old Jacob Philadelphia, touching President Barack Obama's hair in the Oval Office. The boy had wanted to know "if my hair is just like yours." "Why don't you touch it and see for yourself?" replied the president. Souza's photograph showed Obama bending down to let the boy do just that.

Lewis was arguing that the fight to end racial injustice cannot be merely legal or political. It has to involve images and it has to involve culture, because the fight is a struggle for visibility.

Art, of course, is about more than just seeing images of yourself, or people like you, and finding cause for pride in what you see. It is also about seeing others, and about confronting unpleasant, and even horrific realities.

"We do such a good job at closing our eyes to anything that's too dark or too complicated," said the pediatrician Mona Hanna-Attisha in a discussion of the Flint water crisis with Chelsea Clinton. Born in England and raised in Michigan, Hanna-Attisha is the daughter of Iraqi scientists and dissidents and the author of a book about the Flint crisis, "What the Eyes Don't See."

Her research in Flint revealed that, after the water supply was switched from the Detroit River to the Flint River, the city's children were being exposed to unsafe levels of lead. At a 2015 news conference, she urged residents to stop drinking the water. Despite attacks on her credibility, she was vindicated.

Hanna-Attisha argues that, just as lead in water is invisible and does not smell, the residents of Flint - more than half of them African American - were also effectively invisible to those in power.

The effort to confront the baleful truth of mass incarceration is likewise a struggle for visibility. What does mass incarceration look like? The rate of incarceration for blacks in this country is more than five times that of whites. Despite the extreme levels of surveillance prison inmates live with, most of us are blind to the reality of their lives. The atmosphere of fear around prisons only magnifies the effect.

That is why, in the fight to overturn racial bias, "the law won't help us," according to Bryan Stevenson, the celebrated lawyer,and founder of the Equal Justice Initiative. "We're going to need narrative and art and exploration."

In response to an image of Chicago's Harry Weese-designed Metropolitan Correctional Center - a building with a striking and to many people beautiful exterior - Stevenson stressed the need to see beyond the facade.

"We have to reveal the pain and the suffering and the inhumanity that's going on within the building," he said. "If we don't see the people inside, if we don't know that people are being locked down, if we don't know that there might be 10- and 11-year-old children in there - because Illinois doesn't have a minimum age for trying a child as an adult - who are being tormented, if we don't know about the suffering, then we are not going to actually see what's wrong with the building."

Stevenson was discussing the problem with Harvard historian Elizabeth Hinton, the author of an award-winning book on the origins of mass incarceration in America. "It's a question of 'Who gets to be seen as a human being? Who counts?' "

That question - who counts? - was also at the heart of a discussion about the racial prejudices built in to facial recognition technology. "Algorithmic bias," or what poet and digital activist Joy Buolamwini calls "the coded gaze," means that African Americans are often simply not recognized by facial recognition technology. Their genders, too, are frequently misidentified.

If, in the next phase of human society, "data is destiny," as Buolamwini says, the problem of what she calls "pale male data" is fundamental to the question of black visibility.

Data, and the algorithms that harness it, can presumably be tweaked. But data without imagination is a deeper problem. Here again, though, the arts play a vital role. Indeed, if Lewis's roll call of luminaries had anything to teach us, it is that we need not only to open our eyes, but also to use our imaginations.

Visibility is one thing. But in art as in politics, vision - which implies a moral imagination - is where the real action is. As Stevenson said, "You have to be willing to believe things you haven't seen to create justice."