It is hardly an exaggeration to say that a chimpanzee kept in solitude is not a real chimpanzee at all. - Wolfgang Köhler

How ‘real’ it is one feels when trying to form other groups…Most people will never get this other grouping as clear, stable, and optically real as the former one.

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.

[Thinking] respond to an objective constellation of millions of stimuli by developing, first of all, an organised field, many and perhaps the most essential properties of which have no physical partner among the single stimuli.