"Of all the forms of mental activity the most difficult to induce, even in the minds of the young who may be presumed not to have lost their flexibility, is the art of handling the same bundle of data as before, but placing them in a new system of relations with one another by giving them a different framework, all of which virtually means putting on a different kind of thinking-cap for the moment."
Herbert Butterfield, The Origins of Modern Science, 1959
M.C. Escher,
Hand with Reflecting Sphere, 1935.
