In his work On Sense Perception, Aristotle discusses the material conditions of perception, starting with the sense organs and moving to the material basis of colour, flavour and odour. His Pythagorean account of hues as a ratio of dark to light was enthusiastically endorsed by Goethe against Newton as being true to the painter's experience. Aristotle finishes with three problems about continuity. First, in what sense are indefinitely small colour patches or colour variations perceptible? Secondly, which perceptible leap discontinuously like light to fill a whole space, which have to...