…Saturday, October 14, 1972 Ar G., by J o h n Berger. Viking Press, $7.95. By NIGEL GEARING If John Berger now seems Eng- land's most stimulating art cri- tic, it is above all because he has never stopped short at the "mere- ly" aesthetic and the art object per se, because he has never played that game of specialist, fragmented analysis which - in literature as in the visual arts - has kept the universities huh- ming but has too often relegated...…