Solids and Cavities in Architecture
Seeing demands a certain activity on the part of the spectator. It is not enough passively to let a picture form itself on the retina of the eye. The retina is like a movie screen on which a continuously changing stream of pictures appears but the mind behind the eye is conscious of only very few of them. On the other hand, only a very faint visual impression is necessary for us to think that we have seen a thing; a tiny detail is enough.
A visual process can be described as follows. A man walking along with bent head receives an impression of blue jeans; a mere hint will suffice. He believes that he has seen a man though actually all he saw was the characteristic seam running down the side of the leg. From this one small observation he concludes that a man has passed him on the sidewalk, simply because where there is that sort of seam there must be jeans and where there are moving jeans there must be a man inside them. Usually his observation ends here; there are so many things to keep an eye on in a crowded street that he cannot bother his mind with his fellow pedestrians. But for some reason our man wishes to have a closer look at the person. He observes more details. He was right about the jeans but the wearer is a young girl, not a man. If he is not a very dull person he will now ask himself: "What does she look like?" He will then observe her more closely, adding detail to detail until he gets a more or less correct picture of her. His activity can be compared to that of a portrait painter. First he forms a rough sketch of his subject, a mere suggestion; then elaborates it enough for it to become a girl in jeans; finally he adds more and more details until he has obtained a characteristic portrait of that particular girl. The activity of such a spectator is creative; he recreates the phenomena he observes in his effort to form a complete image of what he has seen.