[2] Their growing theoretical disagreements and Schopenhauer's criticisms made Goethe distance himself from his young collaborator.
[3] Although Schopenhauer considered his own theory superior, he would still continue to praise Goethe's work as an important introduction to his own.
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 darkness.
Schopenhauer agreed with Goethe's claim that the eye tends toward a sum total that consists of a color plus its spectrum or afterimage.
In November 1813, Goethe congratulated Schopenhauer on his doctoral dissertation On the Fourfold Root of the Principle of Sufficient Reason which he received as a gift.
A major difference between the two men was that Goethe considered color to be an objective property of light and darkness.
The title was Theoria colorum Physiologica, eademque primaria (Fundamental physiological theory of color).
"This is no mere translation of the first edition," he wrote, "but differs noticeably from it in form and presentation and is also amply enriched in subject matter.
In § 1, it is shown that the perception of externally perceived objects in space is a product of the intellect's understanding after it has been stimulated by sensation from the sense organs.
These remarks are necessary in order for the reader to be convinced that colors are entirely in the eye alone and are thoroughly subjective[10] [11] Intuitive perception, or knowledge of an object, is intellectual, not merely sensual.
This transition from effect to cause is knowledge of the pure understanding, not a rational conclusion or combination of concepts and judgments according to logical laws.
The undivided activity of the retina is divided into stronger or weaker degrees when stimulated by pure light or whiteness.
After staring at a black figure on a white background, the overactive and excited retinal points become exhausted and do not react to stimulation when the eye finally looks away.
The same is true of the seven keynotes in the musical diatonic scale: do, re, mi, fa, sol, la, ti.
When the entire activity of the eye is completely qualitatively partitioned, the color and its spectrum (afterimage) appear with maximum energy as being vivid, bright, dazzling, and brilliant.
For example, the mixture of bright or pale red and green on the same retinal spot results in the impression there of light or white.
The wideness or narrowness of the colored bands are, however, nonessential properties that differ according to the type of light-refracting substance that is used.
In this way, along with the white disk and the black background, four prismatic colors appear: violet, blue, yellow, and orange.
This shows how colors are produced when the image mixes with either lightness or darkness, in accordance with Goethe's assertions.
An additional proof of the subjective nature of color, namely that it is a function of the eye itself and is only secondarily related to external objects, is given by the daguerreotype.
They exist when light combines with cloudy transparent or translucent media, such as smoke, fog, or a glass prism.
Three pairs are distinguished by names of their own, however, because the retina's activity is bipartitioned in a rational proportion that consists of simple numbers.
Unlike Goethe, for Schopenhauer the primary phenomenon, or limit of explanation, is not an external cause, but the "organic capacity of the retina to let its nervous activity appear in two qualitatively opposite halves, sometimes equal, sometimes unequal...."[18][19] Chemical colors are more durable properties of an external object, such as the red color of an apple.
Schopenhauer criticized scientists for thinking that color exists in external objects, instead of in the spectator's eye.
Likewise my theory alone gives the true sense in which the notion of complementary colours is to be taken, viz: as having no reference to light, but to the Retina, and not being a redintegration [restoration] of white light, but of the full action of the Retina, which by every colour undergoes a bipartition either in yellow (3/4) and violet (1/4) or in orange (2/3) and blue (1/3) or in red (1/2) and green (1/2).
Ludwig Wittgenstein and Erwin Schrödinger were strongly influenced by Schopenhauer's works and both seriously investigated color theory.
"[22] The physicist Ernst Mach praised that "men such as Goethe, Schopenhauer" had started to "investigate the sensations themselves" on the first page of his work Die Analyse der Empfindungen und das Verhältnis des Physischen zum Psychischen.
[23] According to Rudolf Arnheim, Schopenhauer's "...basic conception of complementary pairs in retinal functioning strikingly anticipates the color theory of Ewald Hering.
"[24] Nietzsche noted that the Bohemian physiologist, Professor Czermak, acknowledged Schopenhauer's relation to the Young-Helmholtz theory of color.