The Eight and American Modernisms was the latest exhibition that sought to find some kind of unifying thread to bind together eight artists—Arthur B. Davies, William Glackens, Robert Henri, Ernest Lawson, George Luks, Maurice Prendergast, Everett Shinn, and John Sloan—whose formal association lasted roughly a year and whose art has bedeviled the efforts of art historians to assess the importance of their contribution, collectively or as individuals. When the artists banded together in 1908 to...