Berkeley

George Berkeley

George Berkeley made one of the most outrageous claims in the history of philosophy, and the maddening thing is how hard it is to prove him wrong. There is no such thing, he argued, as matter. The solid material world that everyone takes for granted, the stuff out there, independent of any mind, simply does not exist. There are only minds, and the ideas they perceive; the tree, the table, the mountain are nothing but bundles of sensations, colors and shapes and textures, which exist only in so far as some mind is perceiving them. To be, for any object, is to be perceived:esse est percipi. The usual reaction to this is the one Samuel Johnson famously gave, kicking a stone and declaring, "I refute it thus." But Johnson had missed the point completely, and the stone he kicked, the hardness he felt, the ache in his toe, were, every one of them, exactly the sensations Berkeley was talking about, ideas in Johnson's own mind, proving nothing whatever about any "matter" behind them. Berkeley was no crank. He was an empiricist of ruthless consistency, and he had noticed something genuinely unsettling that most people spend their whole lives managing not to notice.

We learn to see. Berkeley began, as a very young man, with a discovery about something as ordinary as eyesight, and it pointed the way to everything after. We assume that we simply see the world out there, in depth, the way a window shows us a street. Berkeley argued that this is an illusion, and a learned one. What the eye actually receives is flat: patches of color and light, a two-dimensional field. Depth, the sense that some things are near and others far, is not given in sight at all; it is something the mind infers, out of long habit, by associating certain visual cues with the experiences of reaching and walking and touching that have always accompanied them. A baby does not see distance; it learns to, by correlating what it sees with what it can grasp. To press the point, Berkeley took up a famous puzzle: if a person born blind, who knows a cube and a sphere only by touch, were suddenly given sight, could they tell which was which just by looking, before touching them? No, Berkeley answered confidently; the seen shapes and the felt shapes are entirely different things, and the link between them must be learned from scratch. When such operations later became medically possible, the patients' confusion proved him largely right. The lesson is the seed of his whole philosophy: perception is far more the mind's own active construction, and far less a passive window onto brute matter, than we ever suspect.

All you ever have is experience. Here is what Berkeley had noticed. Stop and ask what you are actually in contact with, right now. Not the supposed physical object, the chair "in itself," but colors in your visual field, a pressure against your back, a creak when you shift. Everything you have ever experienced, every single thing, has been a perception, an idea in your mind. You have never once encountered "matter," the alleged inert stuff that is supposed to lie behind the perceptions and cause them; by definition you cannot, because the instant you perceive anything at all, it is an idea, not the unperceived matter. So the materialist, Berkeley points out, is in a strange position: he believes passionately in a kind of stuff that, on his own account, can never be seen, touched, tasted, or sensed in any way, a permanently invisible something propping up the world from behind a curtain that can never be drawn. And Berkeley asks the devastating empiricist question: why believe in it at all? It explains nothing the ideas themselves do not already give you, it can never be observed, and the very notion of it, "something that exists entirely unperceived," may not even be coherently thinkable. Strip away that useless ghost, he says, and what are you left with? Exactly the world you actually live in, the world of vivid, orderly experience, missing nothing but a metaphysical fiction you never needed.

The mind that never blinks. But surely, you object, this makes the world absurdly flimsy. If the tree exists only when perceived, does it pop out of existence the instant everyone looks away, and pop back when someone returns? Here Berkeley produces the move that turns his system from a curiosity into a theology, and it is more elegant than its reputation. The tree does not vanish, he says, because there is one mind that never looks away. God perceives all things, always; the whole world is continuously held in being by the divine perception, whether or not any human happens to be attending to it. The cabinet in the empty room does not blink out when you leave; God is perceiving it, and so it persists, ready to meet your senses again, in exactly the state you left it, when you return. More than that: the steady, lawful order of our experience, the way fire always burns and dropped stones always fall, is, for Berkeley, nothing less than the language of God, a coherent system of signs by which the divine mind speaks a stable world into our perceiving minds, moment by moment. So immaterialism, far from being a recipe for chaos, was for Berkeley the firmest possible ground: the world is more reliable, not less, when it rests on the attention of an infinite mind than when it rests on dead, mindless stuff. And so his denial of matter becomes, in his hands, a direct proof of God, who is needed at every instant to keep the world there.

The ghosts of departed quantities. The same fierce demand, that we believe only in what we can clearly conceive, Berkeley turned, with spectacular effect, on the mathematics of his day. The new calculus of Newton and Leibniz was producing miraculous results, but it rested on a slippery trick: it worked with "infinitesimals," quantities supposed to be infinitely small, and in the course of a single calculation it treated these quantities first as real and nonzero, so that you could divide by them, and then, a step later, as exactly zero, so that you could throw them away. In a famous little book, Berkeley pounced. You cannot have it both ways, he said; a quantity cannot be nonzero when you need it to be and zero when you do not. These vanishing infinitesimals he skewered in an immortal phrase, "the ghosts of departed quantities," and he charged the mathematicians, who loved to mock theologians for believing in mysteries, with founding their own science on a mystery just as obscure. He was right. The calculus worked, but its foundations were genuinely incoherent, and it took mathematicians another century of hard labor to put the subject on rigorous footing and finally lay Berkeley's ghosts to rest. A bishop who denied the existence of matter turned out to be the sharpest critic the calculus ever had, which tells you something about the quality of the mind behind the paradox.

The dare you can't refute. The room holds Berkeley's main works, the Principles and the wonderfully readable Three Dialogues, in which a believer in matter and a believer in mind argue it out over three days; cite them by section. It is tempting to file Berkeley under philosophical curiosities, the man with the absurd doctrine you can refute by kicking a stone. But the stone is the joke that has always been on the kicker. His central insight, that all you are ever directly given is experience, and that the "real world behind it" is a posit you can never check against, did not go away when people stopped laughing. The very next great philosopher, Hume, took it and drove it toward a thoroughgoing skepticism; the phenomenalists of the twentieth century rebuilt physics itself as patterns of possible experience; the philosophers of science adopted his suspicion that the unobservable entities of our theories are useful fictions rather than discovered things. And in our own age, when people seriously ask whether the world might be a simulation, whether everything we call reality might be appearances generated and sustained by some mind or machine we can never step behind, they are asking, in modern dress, the exact question Berkeley asked three hundred years ago. He may well have been wrong. But no one has ever cleanly shown how he was wrong, and a philosophy you cannot refute, however badly you want to, is not a curiosity. It is a permanent dare.