"The monument of Klee's obsession with this metaphysics was a singular book, The Thinking Eye, written during his teaching years at the Bauhaus - one of the most detailed manuals on the "science" of design ever written, conceived in terms of an all embracing theory of visual "equivalents" for spiritual states which, in its knotty elaboration, rivalled Kandinsky's. Klee tended to see the world as a model, a kind of orrery run up by the cosmic clockmaker - a Swiss God - to demonstrate spiritual truth.