Conceptual art has been with us for more than fifty years, and it still defines the work of a great many contemporary artists. But what is it? The term “concept art” was first used in 1963 by the philosopher Henry Flynt; it quickly morphed into “conceptual art” and was applied to art work in which the idea behind it is as or more important than the work itself. An early example was Joseph Kosuth’s “One and Three Chairs,” which consisted of a straight-backed chair, a photograph of that chair, and a mounted dictionary definition of the word “chair.” The idea was clear enough, and conceptual artists have been struggling ever since to make works that are not as boring as this one.

Those who succeed have usually been influenced by Marcel Duchamp, the intellectual father of Conceptualism. Duchamp wanted, as he said, to “put art back in the service of the mind.” Leonardo da Vinci described art as a cosa mentale, and that’s what it had been, according to Duchamp, until the nineteenth century, when Gustave Courbet and the Impressionists turned it into something that was purely “retinal,” directed to the eye alone. Rather than attack the retinal consensus, Duchamp, who never bored anyone, undermined it with his “readymades,” common objects (a bicycle wheel, a snow shovel, a bottle-drying rack) transformed into art by the choice of an artist. The readymades defied any attempt to define art, and this turned out to be what contemporary artists needed most—complete freedom to “make it new.” Art became much easier for mediocre artists and a lot harder for good ones. Duchamp spent the last twenty years of his life working in secret on a three-dimensional tableau vivant of a naked, headless female body in a realistic landscape, a strangely disturbing image that is both a summary of his meta-retinal art and a total departure from it.

“I don’t think there’s an artist working today whose head Duchamp hasn’t come into,” Rashid Johnson, an artist in the midst of a groundbreaking career, told me in the spring. “The readymade is part of our critical discourse. When you question art, when you ask the sort of questions that he was able to point us toward, you are forever affected by what he did.”

Johnson, who is forty-seven, grew up in what the curator Naomi Beckwith calls “the first big era of unapologetic Blackness.” His earliest works were made when he was a nineteen-year-old sophomore at Columbia College, in the Chicago suburb of Evanston. Struck by the number of men living on the street in Chicago’s South Side, he would go up to one of them, say what he was doing, ask to take his picture, and offer a few dollars in return. When he had two dozen or so of these images, he took them to the Schneider Gallery in the city and said that he would like to have a show. “I was really cocky,” he remembered. Martha Schneider, the gallery’s owner, looked at the work—closeup portraits of Black men who had withstood decades of hardship and pain—and immediately scheduled an exhibition, called “Seeing in the Dark.” There were no reviews, but the Art Institute of Chicago bought two of the portraits, and the Reader, a popular free newspaper in town, published one of them, titled “Jonathan with Eyes Closed.”

After that, he had three shows at the Monique Meloche Gallery, another Chicago venue, and then, in 2001, the Studio Museum in Harlem put three of his portraits in “Freestyle,” a hugely influential exhibition of work by a new generation of Black artists. Thelma Golden, then the Studio Museum’s chief curator, stirred controversy by describing the “Freestyle” artists as “post-Black,” meaning, as Golden wrote in the show’s catalogue, that these were “artists who were adamant about not being labeled as ‘black’ artists, though their work was steeped, in fact deeply interested, in redefining complex notions of blackness.” (When questioned about the term, Johnson likes to say, “I am currently and presently Black.”) The show included work by Trenton Doyle Hancock, Kojo Griffin, Sanford Biggers, Mark Bradford, Laylah Ali, Julie Mehretu, Camille Norment, and other emerging Black art stars (along with some under-recognized mid-career ones), and it established Johnson as someone to watch. In the years that followed, as Johnson’s work took different forms—videos, sculptures, mosaics, and eventually paintings on canvas—the constant element in all of it was a play of ideas. “I’ve always been more interested in projecting thought into space than in representing the body,” he once said. Using materials and techniques that he invented or rediscovered, he plumbed depths of anxiety and masculine vulnerability that few of his contemporaries had touched, and he did so with full awareness that, in art, ideas went nowhere without compelling visual embodiments that brought them to life.