robert rauschenberg's use of coke bottles, a spare tire, a goat shocked his audience. "if this is art," said one abstract expressionist, "i quit." what's very curious in the history of art is that often the moments where something really decisive happens to change that history, those moments are not terribly perceptible to their contemporaries and only become perceptible in retrospect. i think that one of these moments occurred, at least for our modern sensibilities, with the work of robert rauschenberg and jasper johns. this is a rauschenberg called trophy iii. what rauschenberg does is to insist that the surface of the canvas is no longer a window into which we look or through which we look, a window that opens onto another world as say, this little porthole that i'm looking through that opens onto the skyline of new york. i can see the empire state building through it. rather, what we have is the surface of the canvas as a horizontal field, like a desk top, like the working surface of somebody's studio or somebody's writing table, onto which junk is piled-- mail, po