Moskenstraumen

The heightened sensivety of the picture plane may no longer permit sculptural illusion, or trompe-l'oeil, but it does and must permit optical illusion. The first mark made on a surface destroys its virtual flatness, and the configurations of a Mondrian still suggest a kind of illusion of a kind of third dimension. Only now it is a strictly pictorial, strictly optical third dimension... one into which one can look, travel through, only with the eye.

- Clement Greenberg, "Modernist painting", 1965