Vision is a strange and wonderful business. I have been puzzling over its perplexities for 50 years. I used to suppose that the way to understand it was to learn what is accepted as true about the physics of light and the retinal image, to master the anatomy and physiology of the eye and the brain, and then to put it together into a theory of perception that could be tested by experiments. But the more I learned about physics, optics, anatomy, and visual physiology, the deeper the puzzles got. The experts in these sciences seemed confident that they could clear up the mysteries of vision eventually but only, I decided, because they had no real grasp of the perplexities.
Optical scientists, it appeared, knew about light as radiation but not about light considered as illumination. Anatomists knew about the eye as an organ but not about what it can do. Physiologists knew about the nerve cells in the retina and how they work but not how the visual system works. What they knew did not seem to be relevant. They could create holograms, prescribe spectacles, and cure diseases of the eye, and these are splendid accomplishments, but they could not explain vision.
Physics, optics, anatomy, and physiology describe facts, but not facts at a level appropriate for the study of perception. In this book I attempt a new level of description. It will be unfamiliar, and it is not fully developed, but it provides a fresh approach where the old perplexities do not block the way.
What are its antecedents? I am aware of my debt to the Gestalt psychologists, especially to Kurt Koffka. I have extended many of his ideas. I owe a great deal to the functionalists in American psychology, William James and E. B. Holt, for example. I was influenced in the thirties by Edward Tolman on the one hand, and by Leonard Troland on the other. The doctrine of stimuli and responses seems to me false, but I do not on that account reject behaviorism. Its influence is on the wane, no doubt, but a regression to mentalism would be worse. Why must we seek explanation in either Body or Mind? It is a false dichotomy. As for introspection, so-called, it can be done in the style of David Katz or Albert Michotte without falling into the error of elementarism.
I have learned a great deal from my contemporaries, Robert MacLeod, Ulric Neisser, Julian Hochberg, Ivo Kohler, Fabio Metelli, Hans Wallach, Ernst Gombrich, and especially Gunnar Johansson. My students, too, are my teachers, and since the