“Half or more of the best new work in the last few years has been neither painting nor sculpture,” begins Donald Judd’s essay of 1965, “Specific Objects.” He continues, “The new three-dimensional work does not constitute a movement, school or style.” Judd was speaking of the art of the time, but it’s arguably his own work—which was using industrial materials arranged in a series of different color combinations—that rebelled against simple definition and concurrently created an entirely novel language in modern sculpture. MoMA presents the first U.S. retrospective on this American artist in more than 30 years. —J.V.