On Vision and Colors tried to demonstrate physiologically that color is "specially modified activity of the retina." The initial basis for Schopenhauer's color theory comes from Goethe's chapter on physiological colors, which discusses three principal pairs of contrasting colors: red/green, orange/blue, and yellow/violet. This is in contrast to the customary emphasis on Newton's seven colors of the Newtonian spectrum. In accordance with Aristotle, Schopenhauer considered that colors arise by the mixture of shadowy, cloudy darkness with light. With white and black at each extreme of the scale, colors are arranged in a series according to the mathematical ratio between the proportions of light and
On Vision and Colors that were exhausted by the whiteness become completely inactive. The retinal positions that had been rested are now easily stimulated. This explains afterimage (physiological spectra). Both Goethe and Schopenhauer use the word "spectrum" [Spektrum], from the Latin word "spectrum" meaning "appearance" or "apparition," to designate an afterimage. If, instead of white, we stare at yellow, then the afterimage, or physiological color spectrum, is violet. Yellow, unlike white, does not fully stimulate and exhaust the retina's activity. Yellow partially stimulates points on the retina and leaves those points partially unstimulated. The retina's activity has been qualitatively divided and separated into two