of study in this field to æsthetic problems. But what I do not think has been fully recognized is the fruitfulness of investigation in the perceptual field for the understanding of the part played in our æsthetic response to architecture of its material, that is to say, its dynamic elements. The study of perception is the study of the moulding of our attention, that is, our response and reaction, by the behavior of things. Now architecture (including the minor technical arts, of course) is the art of the behavior of things. Those elements in the complex of perception which depend on response and reaction are immensely reinforced by the real bodily presence of the architectural forms. Thus we may say broadly that the presence of real forces in the object makes a difference in our image of it—makes a difference, speaking 'immediately,' in the object itself. So that the element of structure is directly felt, like distance or solidity.
This is my main point. In the principle that perception of things involves primarily the behavior of objects, lies the possibility of the perfect fusion of our earlier dualism of structure and shape. If shape can be understood—can be taken in at all—only as structure; if perception of structure must involve instinctive response to the forces implicit in that structure, then the way to our sought-for architectural idea is given us. Not that for a moment, of course, are all these facts of forces, thrusts, strains consciously rehearsed, any more than we consciously rehearse our impulse to pick up a stone; but if the stone turns out to be pasteboard, we know in our shock and overbalance that a whole drama of perceptive character has nevertheless been enacted in us. And so, if we look on staff instead of stone—or on huge mushroomy plant forms made up of stone, as in Egyptian architecture, it is for the perceptual psychology to trace to their hidden lair the secrets of our recoils and our tremors, and to show how they bear, in the response they draw from us, or fail to bear, their part in the demanded orchestral harmony of architectural intentions.
So I would say to the experimenter in the field of æsthetics, there lies here before you in the architectural field a whole unworked mine of treasure. How is my perception of objects af-
