The One Thing You Can't Step Outside Of

In November 1619, a young French soldier was stuck indoors somewhere in southern Germany, waiting out the winter with the army he’d signed up for. There was no fighting to do. So he shut himself in a small room warmed by a big stove and spent the whole day alone, doing nothing but thinking. He was twenty-three years old. His name was René Descartes.

He had decided to try something reckless. He was going to doubt everything. Not for fun, and not because he expected to end up believing nothing, but because he wanted to find out whether anything at all could survive being doubted on purpose. So into the fire went the reports of his senses, because senses lie: a straight stick looks bent in water, and every night in dreams the world feels perfectly real until you wake. Into the fire went mathematics too, because maybe some clever deceiver was nudging his mind every time he added two and three. Piece by piece he threw out everything he had ever been taught or shown or told.

And then he hit something that would not go into the fire.

Even to doubt, he had to be thinking. The doubting was itself a thought, and a thought has to be somebody’s. He could pretend the whole world was fake. He could not pretend there was no thinking going on, because the pretending was thinking. “I think, therefore I am.” The one thing that survived the burning of everything else was not something he saw, or heard, or touched. It was the mind catching itself in the act.

Nothing but the senses

Ask most people where their ideas come from, and they’ll tell you something that sounds obviously true: ideas come from experience. The world pours in through the eyes and ears and skin, and the mind fills up with what it receives. You know what red is because you’ve seen red things. You know what a dog is because you’ve met dogs. You start out empty and the world writes on you.

This is not a foolish view. It’s one of the great ideas in the history of thought, and some very careful people have held it. John Locke put it about as plainly as it can be put. The mind at birth, he said, is “void of all characters, without any ideas.” So where does it get everything it later holds? “How comes it to be furnished?” he asks. “Whence has it all the materials of reason and knowledge? To this I answer, in one word, from Experience.” No secret stock of knowledge you were born with. No ideas smuggled in from somewhere else. Just a blank page and a lifetime of sensations filling it in.

There’s an old slogan for this, worn smooth by centuries of use: nothing is in the mind that was not first in the senses. The Aristotelian tradition said it, and thinkers as different as Thomas Hobbes, Locke, and David Hume all signed on in their own ways. It has the ring of plain common sense. Even the fancy ideas seem to obey it. Your idea of justice grew out of seeing fair and unfair things happen. Your idea of a thousand grew out of counting real objects. Peel back any concept, the story goes, and at the bottom you’ll find a pile of things the senses handed you first.

If you’ve been nodding along, good. You’re supposed to. This is the view most of us actually carry around, and it’s worth believing all the way before we touch it. So believe it. The mind is a room, the senses are the windows, and everything in the room came in through a window.

Now the slogan again. Nothing is in the mind that was not first in the senses.

Where did that idea come from?

You never saw it. You never heard “sensation” ring out the way you hear a bell, never tasted “the mind,” never bumped into “experience” walking down the street. The idea that all ideas come from the senses is not itself an idea the senses ever delivered. It came from somewhere the windows don’t open onto. It came from the mind turning around and looking at its own workings. And that turn, it turns out, is a second way of getting ideas, one the tradition kept trying to talk itself out of and kept needing anyway.

The eye that can’t see itself

Start with what the senses can and can’t do.

The senses point outward. That’s their whole design. Your eyes are aimed at the room, your ears at the noise, your fingertips at whatever you’re touching. Sensing is a reaching-out toward something that isn’t you. Plotinus, writing in the third century, put his finger on exactly this. “The mind looks outward,” he wrote of ordinary perception; “this is ample proof that it has taken and takes no inner imprint.” Seeing is a spotlight thrown out onto the world. It is not a photograph the world stamps onto a plate inside you.

And here’s the strange thing about a spotlight: it lights up everything except itself. Your eye can see every object in the room. It can see your own hands. Put a mirror in front of you and it can even see your face. But it can never see the seeing. The eye is the one thing in your whole field of view that you can’t get into your field of view. To look at your own eye, you need a mirror, which means you need something outside the eye to bounce the light back. Left to itself, the eye is invisible to itself.

The same holds for every sense. Your ear can’t hear its own hearing. Your fingertip can’t touch its own touching. As one careful summary of the whole tradition puts it, “it has never been observed that the senses can sense or be aware of themselves.” The senses are wonderful and they are also stuck facing one direction. Out.

So suppose we really do get some ideas by the mind examining what it’s doing, its own remembering and doubting and comparing. Whatever that examining is, it can’t be the outward senses aimed inward, because the outward senses have no reverse gear and their objects are all out in the world. Some thinkers, Locke among them, were tempted to call the inward turn a kind of sense anyway, an “internal sense,” to match it up with seeing and hearing. Call it that if you like. It changes nothing that matters here. Even as an inner channel it is turned the opposite way from the five outward ones, and it reaches things they can’t touch. It is a distinct source, whatever name we hang on it.

The old thinkers split “sense” from “intellect” for a whole tangle of reasons, and most of them don’t matter here. Only one does, and it’s this business of direction. The outward senses go out and stay out. Something else, turned the other way, can come back.

Locke’s second fountain

Here’s where the empiricists give themselves away, and the biggest giveaway comes from the empiricist-in-chief.

Locke said the mind starts blank and fills up from experience. But when he actually sat down to explain how it fills up, he found he could not do it with one source. He needed two. There’s the obvious one, the senses, which he called ideas of sensation: red, loud, cold, sweet, the stuff the windows let in. But alongside it he had to admit a second and very different source, which he called ideas of reflection. These, he said, are “the perception of the operations of our own mind within us, as it is employed about the ideas it has got.”

Read that slowly, because Locke is quietly conceding the whole game. He noticed you cannot build a working mind out of red and loud and cold alone. A person also has ideas of remembering, of doubting, of believing, of choosing, of comparing one thing to another. And you do not get those by looking out the window. There is no color called doubting. There is no sound that memory makes. You get those ideas by the mind watching what the mind is doing. Locke says as much in the same breath, listing the two doors together: our understanding is furnished, he writes, by “observation employed either about external sensible objects, or about the internal operations of our own minds.”

So the great champion of “all ideas come from experience” turns out to believe experience has two doors, and one of them doesn’t open onto the world at all. It opens inward, onto the mind itself. The slogan already has a hole in it, and the hole was punched by the man who did the most to sell the slogan.

Call this second door what Locke did. Reflection. The mind’s habit of turning its attention onto its own acts and contents. And once you notice it’s there, you start to see how much comes through it.

Ideas about ideas

You’ve probably done this in the last hour. You’re reading a page, your eyes keep moving down the lines, and somewhere around the third paragraph you surface and realize you haven’t taken in a single word. You were somewhere else the whole time. That small snap of noticing, the moment you catch that your own attention had wandered off, is reflection happening. It isn’t a sight or a sound. Nothing new came in through a window. It’s an idea about what your mind was just doing, and you made it by swinging your attention around onto the mind itself. You do this constantly, so smoothly you never mark it as strange. It is strange.

Push on it, because reflection isn’t just a second source sitting politely next to the first. It makes a kind of idea the senses could never make, not in a thousand years.

Thomas Aquinas had a sharp way of marking the difference. Most of your ideas, he said, are aimed at things: your idea of a dog is about dogs, your idea of a stone is about stones. He called these the mind’s first business, its “first intentions.” But the mind can also form ideas that are aimed at ideas. Your idea of what an idea is, your idea of doubting, your idea of the mind itself. These he called second intentions: ideas about ideas. And he was clear that they come from the mind bending back on itself. “Since the intellect reflects upon itself,” he wrote, “by such reflection it understands not only its own act of intelligence but also the species by which it understands.”

That word reflects is doing real work, and it’s worth unpacking. Normally a concept is something you look through, not at. Aquinas said a concept “is not what is actually understood, but that by which the intellect understands.” Your idea of “dog” is like a pair of glasses. When you’re using it, you don’t notice it; you notice dogs. The idea is the lens, and the world is what you see through the lens. Reflection is the moment you take the glasses off and look at them. You stop using the concept to think about the world and start thinking about the concept.

And here’s why that new object could never have come in through a window. The thing reflection looks at, your own thinking, judging, meaning, remembering, was never out in the world to be sensed in the first place. Nobody ever saw a judgment lying in a field. Nobody ever heard the sound a meaning makes. These things happen inside the act of thinking, and the only way to get an idea of them is for thinking to turn around and take itself as the subject. First intentions can come from the senses. Second intentions can’t. There’s nothing out there for the senses to grab.

Programmers actually have a name for a system that can stop doing its job and start examining the machinery doing the job. They call it reflection. Same move, same word: the program turns from running the task to reading and even rewriting its own code. It’s a special power, and it’s not the same as ordinary computing. When thought does it, philosophers reach for the same term, because it’s the same trick. The tool turns and looks at the tool.

When the mind studies itself

Which brings us to the sting.

Think about what a science of the mind even is. Every theory of how sensation works, every account of what memory is, every argument about whether the self is one thing or many, all of it is the mind producing ideas about the mind. None of it came in through the senses, because none of its objects were ever out there to sense. A clear summary of the whole tradition says it flatly: theories of sensation “must be regarded as works of reflective thought; they are not products of sensation.” You cannot see a theory of seeing. You have to reflect one into being.

So take the slogan we started believing. Nothing is in the mind that was not first in the senses. If that were true, it could never have been thought at all. It isn’t a sense-idea. Nobody sensed it. It’s a second-intention idea through and through, a judgment the mind made about its own contents by turning around and inspecting them. The doctrine that all ideas come from the senses is a living counterexample to itself. The moment you understand it, you’ve used the very power it says you don’t have.

Now, the strongest objection to all this comes from Hume, and it’s worth taking at full strength rather than brushing off. Descartes trusted that when the mind turns around, it catches a thinker, an “I,” sitting there thinking. Hume went looking for that “I” and couldn’t find it. “When I enter most intimately into what I call myself,” he wrote in his Treatise of Human Nature, “I always stumble on some particular perception or other.” A feeling, a sound, a flash of color, but never the self that’s supposedly having them. He concluded that a person is just a “bundle” of passing perceptions with no owner underneath. So maybe the mind can’t really catch itself after all. Maybe Descartes fooled himself.

But watch what Hume is doing while he says it. He is forming an idea about his own mental operations, namely, that they’re a loose bundle with nobody home. Where did that come from? Not from any sensation. He reached it by turning his attention inward and studying what he found there. His denial of the self is one of the purest acts of reflection anyone has ever written down: an idea about the character of his own ideas, arrived at by watching them work. Hume doesn’t need to find a little self for the point to stand. Reflection was never a matter of the mind spotting a thinker the way you spot a face in a crowd. It’s the mind taking its own acts as the thing it now has an idea about. Hume’s bundle proves the power in the very sentence that empties out the self.

And it’s worth being honest about the limits, because they’re real. This inward turn doesn’t hand us a soul, or a stock of ideas we were born knowing, or a mind that reads itself perfectly. Reflection can be flat wrong. Psychologists Richard Nisbett and Timothy Wilson showed in 1977 that people will confidently report the reasons for their own choices, in detail, when careful experiments prove those weren’t the real reasons at all. The mind is often a poor reporter on itself. But being a poor reporter is not the same as not being a source. The senses fool us too. The stick still looks bent in the water; the mirage still shimmers on the road. We don’t conclude from that that sight gives us no ideas. We conclude that a source of ideas can also be a source of mistakes. The claim here is narrow, and it survives every one of these objections: the mind’s examination of its own acts is a real source of ideas, and it is not a source the senses can stand in for. Whatever the mind finally turns out to be, even if it’s nothing but the brain doing its work, this turning-inward is something the outward-facing senses simply cannot do.

Back in the stove-heated room

Descartes, alone with his stove in that cold winter, was not staring at some little self floating in his private view. There was no inner object he glimpsed and pointed to. What he found was the act. The mind, for once, bending all the way back and catching what it was doing. His bedrock wasn’t anything he perceived. It was the turning-around itself, the one move no eye, no ear, no hand can make.

You will spend your entire life unable to step outside your own mind and check it against the world from some neutral place. There isn’t one. That’s the cage. It is also the only reason you will ever understand a mind at all, including the one reading this sentence right now.