In the upper center of Braque's first collage, Fruit Dish (in Douglas Cooper's collection), a bunch of grapes is rendered with such conventionally vivid sculptural effect as to lift it practically off the picture plane. The trompe-l'oeil illusion here is no longer enclosed between parallel flatnesses, but seems to thrust through the surface of the drawing paper and establish depth on top of it. Yet the violent immediacy of the wallpaper strips pasted to the paper, and the only lesser immediacy of block capitals that simulate window lettering, manage somehow to push the grape cluster back into place on the picture plane so that it does not ``jump.'' At the same time, the wallpaper strips themselves seem to be pushed into depth by the lines and patches of shading charcoaled upon them, and by their placing in relation to the block capitals; and these capitals seem in turn to be pushed back by their placing, and by contrast with the corporeality of the woodgraining. Thus every part and plane of the picture keeps changing place in relative depth with every other part and plane; and it is as if the only stable relation left among the different parts of the picture is the ambivalent and ambiguous one that each has with the surface. And the same thing, more or less, can be said of the contents of Picasso's first collage.

In later collages of both masters, a variety of extraneous materials are used, sometimes in the same work, and almost always in conjunction with every other eye-deceiving and eye-undeceiving device they can think of. The area adjacent to one edge of a piece of affixed material -- or simply of a painted in form -- will be shaded to pry that edge away from the surface, while something will be drawn, painted or even pasted over another part of the same shape to drive it back into depth. Planes defined as parallel to the surface also cut through it into real space, and a depth is suggested optically which is greater than that established pictorially. All this expands the oscillation between surface and depth so as to encompass fictive space in front of the surface as well as behind it. Flatness may now monopolize everything, but it is a flatness become so ambiguous and expanded as to turn into illusion itself -- at least an optical if not, properly speaking, a pictorial illusion. Depicted, Cubist flatness is now almost completely assimilated to the literal, undepicted kind, but at the same time it reacts upon and largely transforms the undepicted kind -- and it does so, moreover, without depriving the latter of its literalness; rather, it underpins and reinforces that literalness, re-creates it.