Elsewhere I have spoken of the fact that many artists, especially modern ones, see nature as an arrangement of colored spaces or masses in relation to one another. This implies that they are very little conscious of the edges or outlines of the masses. If they think of them at all, it is to try and prevent your noticing them in their pictures. They paint, for example, the head, and shoulders, and cheek of a man, a bust portrait--with a dark background. If you examine the picture closely, you will not find a sharp line, separating the head from the background. In fact the color of the hair and cheek seems to extend a little way into the dark of the background. The artist has dragged his brush round the head, so that it is impossible to say just where the background begins. The reason for this you understand, as soon as you step back and look at the picture from a short distance off. The head appears very solid; we can believe there is really a hard skull beneath the full flesh of the cheeks and the tight skin of the forehead. Yet the head does not seem to be stuck against the background, like a postage stamp on an envelope. Indeed, if the picture is well painted, the dark part is not really a background. That is to say, it is not merely something behind the head; it seems to have depth and to go back, but it also comes forward and surrounds the head. The latter does not stick out of the picture, it keeps its place back within the frame, enveloped in atmosphere that, though it is very dark, is penetrable. You feel, that is to say, that your hand could be pushed through it without coming up against some wall, as it were, that would stop it.