Why is the sky blue?

Kupferschmidt’s statement that “blue light is not actually blue,” expresses a conviction that is widely shared by writers, physicists, educators, and many other voices. It amounts to a definition of what color is. Blue light, and all other colored light, is said to be merely particular wavelengths. The word merely is expressive. It means that colors have no reality, that we only see things as colored, and that a colorful world is not the real world. This understanding of color denies that human experience is the basis for all knowing. Doubt about human experience is a most deeply ingrained prejudice of modern western societies, and it is their bane, estranging us from the world we live in and from ourselves. In a time when virtual reality has become a dominant part of our experience, and when questions about “fake news” and “fact checking” have become pressing, the question whether we can rely on our experiences as encounters with a real world is of heightened urgency. Centuries-long philosophical and natural scientific debate and reasoning seem to deny that the world we perceive and experience is real. However, there is a glaring inconsistency in the reasoning. People who speak like Kupferschmidt take the brain to be real. They take the instruments used for researching brain activity for real, as well as the researcher’s actions, interventions, and measurements. They take to be real everything that led to the science of electromagnetic radiation and photons with particular wavelengths. When they then come to the conclusion that brain activity is real but the perception of color is not, the reasoning becomes unreasonable. They declare one set of observations to be real, another set of observations to be unreal. When you question sense perceptions, you must also question the sense perceptions, observations, and measurements involved in brain research. The claim that denies reality to sense perceptions undermines and destroys the foundation of all natural science. If color as perceived is not real, then the brain as perceived and the measuring instruments as perceived are also not real. The late philosopher Ronald Brady argues that the statement that one class of observations (those of brain functions as observed by neuroscience) should be set apart from all other observations — like color, taste, sound, warmth, touch, balance, and so on — is not a result of experiencebased science but the result of a preference for a worldview. It is believed, but not substantiated by observation.3 Once we realize that in science we cannot shun sense experience, that the basis of all knowing is human experience, we do not ask what “is behind” and “causes” color. We do not set the class of phenomena relating to electromagnetic radiation and brain research, or any other class of phenomena, above and against the class of visual phenomena. Phenomena relate to each other, certainly, but they do not cancel each other out, the one being real, others not being real. How phenomena relate to phenomena is the question of research rooted in experience. It is here that we meet hindrances and our own limitations. We need to ask ourselves: What underlying preferences help to shape our judgments? What are our hidden assumptions? What are our rigid thought forms? What are our conceptual limitations? How can color research based on phenomena unfold? Phenomena inform and modify our knowledge. By attending to appearances of color in the world, the question “Why is the sky blue?” becomes the question “Where and how does the color blue appear?” No t e s a n d R e v i e w s