Goethe and Color

Over at Pure Pedantry, Kara has a nice post on Goethe and game theory. While we're on the topic of Goethe's prescience, I'd thought I'd mention one of Goethe's most important scientific contributions: his analysis of color. Simply put, Goethe argued that our perception of color is a phenomenon of the brain rather than of physics.

By insisting that color be seen in its psychological context, Goethe was critiquing the science of Isaac Newton, who saw color in terms of discrete wavelengths of light which the eye passively received. Newton believed that color could only be understood by understanding the "least parts" of light. He imagined light as "corpuscular," composed, like glowing dust, of invisibly small particles "emitted from shining substances." By making light a material thing, Newton was able to subsume even the photon - the most ethereal of God's elements - into the laws of his physics. Light, like a planet, was subject to the newly invented force of gravity.

But Newton knew that science required a story. Truth must be seen to emerge from carefully negotiated experiments. And so, in his Optiks, Newton adroitly described his "proof" of light's substance, narrating his method in one of the most famous scientific experiments of all time. Wielding only a prism (or so the story goes), Newton described how he created a perfect rainbow out of white light, the rainbow composed of neat and distinct shades. This made perfect sense to Newton, since every color we perceive was itself a separate wavelength, a unique property bestowed upon the universe by a mathematical God. Using a second prism, Newton showed how these spectral colors could be recombined into the original white light.

On closer inspection however, Newton's data in his experiment cruces seems a little too precise. No one can see what Newton said he saw, since the colors of the rainbow blur into each other. Newton said he was able to distinguish seven primary colors, although his only reason for choosing seven seems to be that a musical octave had seven tones. (Newton wanted nature to be simple.)

But by privileging his hypothesis over his data, Newton willfully ignored a fascinating truth about the mind: it corrupts. While white light is, of course, composed of different wavelengths, the eye does not perceive color in the terms of Newtonian physics. The seven colors broken by Newton's prism out of white were in fact perceived by Newton's brain probabilistically, not perfectly. His brain - and not God - had invented his sensation of color.

Goethe was the first to realize that Newton had oversimplified things . In his 1400 page treatise on color, Zur Farbenlehre, which he was busy writing from 1793 until 1810, Goethe believed he had uncovered a scientific truth that would outlast his poetry: "I do not pride myself at all on the things I have done as a poet. There have been excellent poets during my lifetime; still more excellent ones lived before me, and after me there will be others. But I am proud that I am the only one in my century who knows the truth about the difficult science of color."

As Goethe describes it, his epiphany on the perception of color happened as he "was walking in a garden, upon an April day, looking at the yellow crocuses. To my astonishment, I noticed that turning my eyes to the ground, I then saw violet spots." After reflecting on his flowers and their violet chimera, Goethe decided to delve into the paradox. He began as Newton had: with a prism, a window, and a white wall. But unlike Newton, Goethe saw no rainbow. "The wall remained as white as before," he wrote in his scientific notebook, "and that only there, where an opaque interfered, could a decisive color be observed." Goethe realized that to "produce a color a limit was needed, and instinctively I exclaimed 'Newton's theory is false!'"

The "limit" color needed before it could exist was the mind. Colors, said Goethe, were a side effect of the brain's mechanics, emerging in tandem with other variables, like brightness and shadow. This simple insight meant that Newton's physics - since it saw color as an absolute - was unable to fully explain our sensations. Furthermore, Goethe held that the eye only perceived three colors (red, yellow and blue) and not the seven displayed by Newton's prism. Goethe declared as his credo that "optical illusion is optical truth."

Newton's error in his color theory, said Goethe, was trusting math over the sensations of his eye. "Insofar as he makes use of his healthy senses," wrote Goethe, "man himself is the best and most exact scientific instrument possible. The greatest misfortune of modern physics is that its experiments have been set apart from man." Goethe wanted to correct Newton's false abstractions. If Newton began with the equation, he would begin with the eyeball, with a "physiology of color." He would return color to its beginning, in the brain.

Essentially, Goethe and Newton simply saw color from two separate perspectives. Color is both a variable of physics and a creation of our mind. But when it concerns the sensation of color, Goethe was right. Without knowing the details, Goethe realized that the cones in our retina express only a preference for a tint; they are guided by no real sense of exactitude. While light exists in a literal infinity of different wavelengths, there is no cell in your eye that fires only in response to any specific wavelength. Instead, our eye is densely populated by three classes of cone photoreceptors with overlapping spectral sensitivities. Each kind of cone is tuned to a particular kind of light, which they absorb with a greedy efficiency. For example, short-wavelength cones (S) peak somewhere around violet, while long-wavelength cones (L) love a languid yellowness. But while every cone has its favorite slant of light, they all still respond to vast swaths of the spectrum. As a result, before we can see anything the mind must interpret the retina's vague data. Our visual cortex takes the imprecise input of the eye and transforms it into a colorful chimera. And though Goethe would never figure out exactly how the brain makes the rainbow, he never gave up trying. His last words? "More light".

This is a painting by J.M.W Turner, entitled Light and Color (Goethe's Theory).