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
White point chromaticity diagram, it can be seen that almost all non-spectral colors (all except those on the line of purples), including colors described as white, can be produced by "infinitely many" combinations of spectral colors, and therefore by infinitely many different illuminant spectra. Although there is generally no one-to-one correspondence between illuminants and white points, in the case of the CIE D-series standard illuminants, the spectral power distributions are mathematically derivable from the chromaticity coordinates of the corresponding white points. Knowing the illuminant's spectral power distribution, the reflectance spectrum of the specified white object (often taken as unity), and the numerical