Wolfgang Köhler

"For the most part similarities of various degrees will occur in one perceptual situation; and then specific perceptual units will be formed not simply because their members resemble each other, but because their mutual resemblance is greater than is that of such members and any other parts of the situation."

"I do not deny that objective experience is imbued with acquired meaning in many respects... Probably no experience escapes from the influence of meaning."

"Our present knowledge of human perception leaves no doubt as to the general form of any theory which is to do justice to such knowledge: a theory of perception must be a field theory. By this we mean that the neural functions and processes with which the perceptual facts are associated in each case are located in a continuous medium."

"At the present time it is of course quite customary for physicists to trespass on chemical ground, for mathematicians to do excellent work in physics, and for physicists to develop new mathematical procedures... Trespassing is one of the most successful techniques in science."

"At a given time some concrete forms are simply there in vision, not less than colors and brightnesses."

"For adult man with his mechanized methods of solution, proof is sometimes needed, as here, that an action was a real achievement, not something self-evident; that the breaking off a branch from a whole tree, for instance, is an achievement over and above the simple use of a stick, is shown at once by animals les"