Well, there is a controversy online today. What color is this dress?

Well, it turns out—some people see it as blue and black, while others see it as white and gold. Despite the Internet memes, how you see it tells you nothing about whether you are depressed, manic, crazy, or whatever. But people do see it differently. It simply has to do with differences in the way our eyes process light and our brains process visual information. Surprise, surprise: we don't do it all exactly the same—especially when the wavelengths of light we are processing are on the borderline between two different colors. Lighten the image, and it will look more obviously white and gold. Darken the image, and it will look more obviously blue and black.

The fact that some people see it differently shouldn't be any more surprising than the fact that some people are colorblind or the fact that our senses can be fooled by optical illusions, like this one:  

WIRED explained the science behind why people see the dress different quite nicely, but there are also some philosophical lessons to be learned.

First of all, this is just one of hundreds of examples of how our senses simply are not as reliable as we think they are. Not only is the information our senses receive sometimes deficient, but our senses simply have to interpret the information they receive as best they can—and they quite often don't do that great of a job. Most often, our senses are simply making guesses based on surrounding information and context clues. Frequently, we will simply see or perceive what we expect to perceive—or even what we want to perceive.

This is why one of the basic rules of critical thinking is this: "just because something seems to be true doesn’t mean that it is true.” We always have to wonder whether our senses have led us astray due to less than ideal environmental conditions or because of our biases and expectations. This is why people rooting for different teams will have different opinions about whether something counts as a foul (they can literally see the event differently). This is why seeing a "ghost" in a poorly lit house that you have been told is haunted is not a good reason to actually think ghosts exist.

But the second lesson to be learned is about the way the world is. The WIRED article mentioned above concludes by suggesting that people who see the dress as white and gold are "utterly, completely wrong." In other words, they’re suggesting that the dress really is blue and black. They say this because when you pull the colors off the image and find where they fall on the color palette, you will find that they fall under the blue and black spectrum. But they're wrong. Not because "that's not where the colors fall on the palate" or because "the dress is really white and gold." It's because the dress is not any color at all!

Think about it. Why do we see the colors that we see? Why do we see a leaf as green? Well, ultimately, it's because the neurons in our brains fire a certain kind of way. But it's not like the neurons are green. They just produce a green experience.

Now, the neurons fire the way they do because of electrical signals that are sent to them by the eyes, but electrical signals aren't colors either—they’re just, roughly put, moving electrons. And your eyes send the signals they do because of the way wavelengths of light interact with their rods and cones. But, again, it's not like different wavelengths of light are actually different colors.

That may seem strange because we often divide different wavelengths into different colors. But the difference between wavelengths of light is simply (roughly speaking) the distance between their photons. The photons in high-frequency light are close together, and the photons in low frequency light are far apart. (For ease of explanation, I’m ignoring the particle/wave duality of light.) But photons don't change color based on their proximity to other photons; they aren't even a color at all. After all, when you walk outside during the day, every inch of space around you is filled with photons—but it’s not like you see any of them. You see things like buildings and trees instead.

Now, you see the leaf as green because it absorbs certain wavelengths of light and reflects others. The fact that it reflects a wavelength between 495 to 570 nm is why you see it as green. But what causes it to reflect that wavelength is not its “being a certain color.” It’s ultimately because its molecular structure interacts with light in a certain way—a way such that some frequencies are absorbed and others are reflected. But "molecular structure" is not a color.

And so, when you look at a leaf, the leaf itself is not green; it simply reflects a wavelength of light that causes your eyes to send a signal to your brain that produces a green experience. All things considered, the only thing that is actually green is your experience of the leaf. The leaf is not a color at all. It just causes you to have a certain kind of experience.

So, the controversial picture of the dress is not blue/black, nor is it white/gold—it is neither. It’s not any color at all. There is an objective fact about what wavelength of light it emits from your computer screen, but that wavelength of light is interpreted in different ways by different brains. Even if it's the case that most people interpret that wavelength, in that context, as blue/black, the proposition "the dress is blue and black” is no truer than the proposition "the dress is white and gold." Both propositions are false since the dress is actually no color at all. The only true propositions are about what kind of experiences the picture of the dress produces in different people.

And this is nothing new. The philosopher John Locke identified this distinction long ago when he delineated between primary and secondary qualities. Primary qualities are qualities that objects have regardless of whether you're perceiving them. Secondary qualities are qualities that objects only have in virtue of how we perceive them. And color is the quintessential example of a secondary quality.

Look. I'm not a relativist; I'm not saying there is no way the world is. There are definite facts about the world and they are discoverable. But, the fact is, the dress is not a color. The only thing that is blue and black or white and gold is people's experiences.

But I will say that disagreements about the color of the dress, and how vitriolic they have gotten—everyone who disagrees with you is an idiot, a moron, or whatever—are the perfect analogy for our disagreements in politics, religion, and even ethics. Maybe there is no fact of the matter on these issues; people just see the world differently.

Copyright (2015), David Kyle Johnson

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