Theory of Colours
Goethe delivered in full measure what was promised by the title of his excellent work: Data for a Theory of Color. They are important, complete, and significant data, rich material for a future theory of color. He has not, however, undertaken to furnish the theory itself; hence, as he himself remarks and admits on page xxxix of the introduction, he has not furnished us with a real explanation of the essential nature of color, but really postulates it as a phenomenon, and merely tells us how it originates, not what it is. The physiological colors … he represents as a phenomenon, complete and existing by itself, without even attempting to show their relation to the physical colors, his principal theme. … it is really a systematic presentation of facts, but it stops short at this. (Schopenhauer, On Vision and Colors, Introduction)