All art that is expressive has to be illusionistic. The raw material out of which art is built is not necessarily in itself potent; you must transform it. Contours, tactility, touch, color, intervals, that's all part of the concreteness of art. You have to make the concreteness expressive. That way you don't cater to taste. You resist sentimentality. Things in a picture can't remind you too much of anything else. You have to resist all that.