Is There A Real World Out There?

Here’s a commonsense view of perception. Let’s call it the “how things seem” view.

There’s a mind‑independent reality out there, full of objects and people and places that actually have properties like color, shape, texture, and so on. Our senses act as transparent windows onto this world, detecting these objects and their features and conveying this information to the brain, whereupon complex neuronal processes read it out to form perceptions. A coffee cup out there in the world leads to a perception of a coffee cup generated within the brain. As to who or what is doing the perceiving—well, that’s the “self,” isn’t it, the “I behind the eyes,” one might say, the recipient of wave upon wave of sensory data, which uses its perceptual readouts to guide behavior, to decide what to do next. There’s a cup of coffee over there. I perceive it and I pick it up. I sense, I think, and then I act.

This is an appealing picture. Patterns of thinking established over decades, maybe centuries, have accustomed us to the idea that the brain is some kind of computer perched inside the skull, processing sensory information to build an inner picture of the outside world for the benefit of the self. This picture is so familiar that it can be difficult to conceive of any reasonable alternative.

LUDWIG WITTGENSTEIN: “Why do people say that it was natural to think that the sun went round the Earth rather than that the Earth turned on its axis?”

ELIZABETH ANSCOMBE: “I suppose, because it looked as if the sun went round the Earth.”

LUDWIG WITTGENSTEIN: “Well, what would it have looked like if it had looked as if the Earth turned on its axis?”

In this delightful exchange between Wittgenstein and his fellow philosopher (and biographer) Elizabeth Anscombe, the legendary Austrian thinker uses the Copernican revolution to illustrate the point that how things seem is not necessarily how they are. Although it seems as though the sun goes around the Earth, it is of course the Earth rotating around its own axis that gives us night and day, and it is the sun, not the Earth, that sits at the center of the solar system. Nothing new here, you might think, and you’d be right. But Wittgenstein was driving at something deeper. His real message for Anscombe was that even with a greater understanding of how things actually are, at some level things still appear the same way they always did. The sun rises in the east and sets in the west, same as always.

As with the solar system, so with perception. I open my eyes and it seems as though there’s a real world out there. Today, I’m at home in Brighton. There are no cypress trees like there were in Santa Cruz, just the usual scatter of objects on my desk, a red chair in the corner, and beyond the window a totter of chimney pots. These objects seem to have specific shapes and colors, and for the ones closer at hand, smells and textures too. This is how things seem.

Although it may seem as though my senses provide transparent windows onto a mind‑independent reality, and that perception is a process of “reading out” sensory data, what’s really going on is—I believe—quite different. Perceptions do not come from the bottom up or the outside in, they come primarily from the top down, or the inside out. What we experience is built from the brain’s predictions, or “best guesses,” about the causes of sensory signals. As with the Copernican revolution, this top‑down view of perception remains consistent with much of the existing evidence, leaving unchanged many aspects of how things seem, while at the same time changing everything.

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Anil Seth is professor of cognitive and computational neuroscience at the University of Sussex. Excerpt above from his book, Being You.