Robert Morris—the American artist who, as a founding practitioner of Minimalism, irreversibly transformed contemporary art—has died at age eighty-seven in Kingston, New York, from pneumonia, according to his wife, Lucile Michaels Morris. For over five decades, Morris flouted predictability through his experimentations in sculpture, dance, performance, installation, Land art, and process art.

Born in Kansas City, Missouri, in 1931, Morris studied painting at the Kansas City Art Institute before serving in the Army Corps of Engineers. He then went on to study philosophy at Reed College in the early 1950s. In 1959, Morris moved to New York City with his then-wife, Simone Forti, who would become one of contemporary dance’s most innovative figures and with whom he participated in the Judson Dance Theater. He swiftly rose to fame after exhibitions at Green Gallery in 1963 and 1964 that featured humble geometric forms, such as gray plywood cubes and beams that upended viewers’ presumptions about art and caught the attention of fellow Minimalist artist and critic Donald Judd.

In 1964, Morris became a professor of art at Hunter College, where he stayed for three decades. In 1966—the same year he partook in the Jewish Museum’s watershed “Primary Structures” exhibition, curated by Kynaston McShine—Morris published a series of provocative essays in Artforum titled “Notes on Sculpture,” in which he contextualized Minimalist art as being dependent on the context of its creation. Beginning in the late ’60s, Morris continued to trouble art’s possibilities through his involvement in the post-Minimalism movement, which he championed in his Artforum essays “Anti-Form” (1969) and “Notes on Sculpture, Part IV: Beyond Objects” (1969). His oeuvre encompassed myriad forms and materials; Morris worked with aluminum, wood, mirrors, video, the human body, rags, felt, and earth—the latter most notably in Observatory, 1977, in Holland. During the 1980s, he swiveled to figurative painting with pieces that addressed nuclear anxiety.

“It is rare to find members of Morris’s generation making such energetic work,” wrote the late Artforum contributor Robert Pincus-Witten in a 2015 review of his work at Leo Castelli Gallery, where Morris showed throughout most of his career. “Most, if not having already left the scene, create nothing more than the repetition of signaturized merchandise designed to resurrect the aura of discoveries long past. That has never been Morris’s way.”

The artist’s work has been exhibited widely and resides in permanent collections around the world. New fiberglass and fabric pieces are currently on display at Leo Castelli Gallery’s Midtown location in a show titled “Banners and Curses.” A collection of his essays, Continuous Project Altered Daily, was published by MIT Press in 1993. “Paradox and the fugitive were always more attractive than assured style and stable position,” Morris wrote in his introduction to the book. “Rupture and disruption, not any organic development, provided the dynamic.”