IS REALITY A DIRTY WORD? By Martin Gardner Reprinted from American Journal of Physics Volume 57 March 1989 page 203 Every now and then a philosopher is smitten with incredible hubris. "Man is the measure of all things" was how Protagoras vaguely put it. For some metaphysicians, mostly in Germany, hubris mounted to such heights that they imagined the very existence of the universe depended on human minds. Only our shifting perceptions are real. If we cease to exist, presumably the universe would dissolve into structureless fog, perhaps cease to exist altogether, perhaps never to have existed. Laws of science and mathematics, the structures of fields and their particles, are not "out there." They are free creations of the human spirit. Instead of seeing our brains as feeble, short-lived ensembles of atoms dancing to universal rules, this curious view sees our brains as actually inventing physical laws-in a sense, constructing the universe. J. J. Thomson did not discover the electron. He invented it. Einstein did not discover the laws of relativity, he fabricated them. The fact that such fabrications are so successful in explaining past observations and predicting future ones strikes a cultural solipsist as uncanny, inscrutable magic. "The Unreasonable Effectiveness of Mathematics" was the title of Eugene Wigner's best-known essay. Now there is nothing unusual about philosophers holding such opinions because no view is so bizarre that some metaphysician hasn't defended it. The astonishing thing is that in recent years a few working physicists have abandoned the realism of Newton and Einstein. "The purpose of this article is to refute the fallacy that reality exists outside of us," writes British physicist Paul Davies in his contribution to "The Encyclopedia of Delusions". The theme of astrophysicist Bruce Gregory's "Inventing Reality: Physics as a Language" is accurately described on the books flap: "Physicists do not discover THE physical world, they invent A physical worldSas the poet Muriel Rukeyser puts it 'The universe is made of stories, not of atoms.'" For decades, John Wheeler has been telling us that sentient life exists nowhere in the universe except on little old Earth; that if the universe had not been structured so as to allow itself to be observed by us, it would have only the palest sort of reality. "Quantum mechanics," he asserts, "Sdemolishes the view that the universe exists out there." Frank Wilczek, reviewing a recent book honoring Wheeler (Science, 28 October 1988) diplomatically comments on this remark: "The importance of Wheeler's technical contributions to physics gives his statements a weight that, coming from another source, they would not have." It is a short step from Wheeler's social solipsism to the notion that science is not a progressively better understanding of eternal laws, but a cultural creation like music and art. Competing scientific theories are "incommensurable," varying from place to place and time to time like fashions in clothes. You can no more say one is true and the others false than you can say that one nation's traffic laws are superior to those of another. It is a view held mainly by social scientists, unable to escape from cultural relativism, who look for support to historian Thomas Kuhn and philosopher Paul Feyerabend. Physicists influenced by New Age nonsense, and by what they fancy certain Eastern religions say, find the strongest support for antirealism in the "measurement problem" of quantum mechanics. A particle's property seems not to be out there until the particle interacts with a measuring apparatus that collapses its wave packet and allows the property to become "definite." Because all material things, including measuring devices, are ensembles of particles, it seems to follow that they too are not there until some one observes them. "To be is to be perceived," said George Berkeley, but the canny Irish bishop generously restored the external world by allowing God to observe it. Cultural solipsists, unwilling to call on God, are left with what Wheeler calls a "participatory universe"-one whose reality depends on our cooperation in experiencing it. Does it follow from the fact that an electron is not there until observed that the universe is not there until observed? It does not. There is nothing new about the fact that many things that seem to be out there are not. The image in a mirror is not behind the mirror, as baby chimps suppose. No two persons in front of a looking glass see the same reflection. A mirror does not look like anything in an empty room. It does not follow that a well-defined structure of room, mirror, and bouncing light rays is not there. A rainbow is observer dependent. No two people see the same bow. No arc of colors is out there. It does not follow that a well-defined structure of Sun, sunlight, and raindrops is not there. Moreover, neither rainbow nor mirror images require human observation. Unmanned cameras photograph them admirably. It is true that an electron is somehow-no one knows exactly how-not there until measured even though the measurer can be mindless. It does not follow that the macroscopic records of measuring instruments are not there, as Wigner and some parapsychologists maintain, until a human mind sees them. It does not follow that quantum fields, interacting in enormously complex ways, are not there. Because the sound of a falling tree is a sensation in your brain, it does not follow that the tree and the compression waves are inside your brain. Quantum mechanics raises not a single fresh metaphysical problem. It has nothing to say about such ancient unanswerable questions as whether the universe was created or exploded all by itself, whether it would go on running if all minds vanished, or why quantum fields exist rather than nothing. If you are compelled to think, for emotional reasons or because some guru said so, that you are essential to the universe, that the Moon would not be there without minds to see it (the mind of a mouse? Einstein liked to ask), you are welcome to such self-centered insanity. Don't imagine that it follows from quantum mechanics. Realism is not a dirty word. If you wonder why all scientists, philosophers, and ordinary people, with rare exceptions, have been and are unabashed realists, let me tell you why. No scientific conjecture has been more overwhelmingly confirmed. No hypothesis offers a simpler explanation of why the Andromeda galaxy spirals in every photograph, why all electrons are identical, why the laws of physics are the same in Tokyo as in London or on Mars, why they were there before life evolved and will be there if all life perishes, why all persons can close their eyes and feel eight corners, six faces, and twelve edges on a cube, and why your bedroom looks the same when you wake up in the morning. =======================================================