Pop art was no less startling an assault; however its heresies, like those of Abstract Expressionism, became familiar pieties and soon evoked respectable ancestors, so that Lichtenstein, for example, now looks quite as solemnly museum-worthy as Leger or Stuart Davis, who, in turn, must first have looked as brashly unprecedented as the Pop artists. And Earth Works, which seemed to undermine even the material con ventions of Western art, have taken on, now that the dust has settled, a historical resonance that permits us to think of the best of them as, among other things, noble efforts to syn thesize the grandest powers of man and nature in a geographic union that recreates, in late twentieth-century terms, our deepest Western memories of monuments as remote andawesome as Stonehenge or the Pyramids of Giza.