Foucault’s injunction to historians quoted in the epigraph has immediate and literal relevance to the study of painting in New York during the 1940s. If we are in the midst of “redefining” or “reappraising” that art, as it has become fashionable to contend, an examination of the conventional categories structuring our understanding of the period would seem a necessary part of that process. The central category is, of course, Abstract Expressionism, or the New York School. Redefinition …