What Physics Learns From Philosophy

A KERFUFFLE has broken out between philosophy and physics. It began earlier this spring when a philosopher (David Albert) gave a sharply negative review in this paper to a book by a physicist (Lawrence Krauss) that purported to solve, by purely scientific means, the mystery of the universe’s existence. The physicist responded to the review by calling the philosopher who wrote it “moronic” and arguing that philosophy, unlike physics, makes no progress and is rather boring, if not totally useless. And then the kerfuffle was joined on both sides.

This is hardly the first occasion on which physicists have made disobliging comments about philosophy. Last year at a Google “Zeitgeist conference” in England, Stephen Hawking declared that philosophy was “dead.” Another great physicist, the Nobel laureate Steven Weinberg, has written that he finds philosophy “murky and inconsequential” and of no value to him as a working scientist. And Richard Feynman, in his famous lectures on physics, complained that “philosophers are always with us, struggling in the periphery to try to tell us something, but they never really understand the subtleties and depths of the problem.”

Why do physicists have to be so churlish toward philosophy? Philosophers, on the whole, have been much nicer about science. “Philosophy consists in stopping when the torch of science fails us,” Voltaire wrote back in the 18th century. And in the last few decades, philosophers have come to see their enterprise as continuous with that of science. It is noteworthy that the “moronic” philosopher who kicked up the recent shindy by dismissing the physicist’s book himself holds a Ph.D. in theoretical physics.

Physicists say they do not need any help from philosophers. But sometimes physicists are, whether they realize it or not, actually engaging in philosophy themselves. And some of them do it quite well. Mr. Weinberg, for instance, has written brilliantly on the limits of scientific explanation — which is, after all, a philosophical issue. It is also an issue about which contemporary philosophers have interesting things to say.

Mr. Weinberg has attacked philosophical doctrines like “positivism” (which says that science should concern itself only with things that can actually be observed). But positivism happens to be a mantle in which Mr. Hawking proudly wraps himself; he has declared that he is “a positivist who believes that physical theories are just mathematical models we construct, and that it is meaningless to ask if they correspond to reality.” Is Mr. Hawking’s positivism the same positivism that Mr. Weinberg decries? That, one supposes, would be an issue for philosophical discussion.

The physicist Sir Roger Penrose is certainly not a positivist. He is a self-avowed “Platonist,” since he believes (like Plato) that mathematical ideas have an objective existence. The disagreement between Mr. Hawking the positivist and Mr. Penrose the Platonist — a philosophical one! — has hard scientific consequences: because of it, they take radically opposed views of what is going on when a quantum measurement is made. Is one of them guilty of philosophical naïveté? Are they both?

Finally, consider the anti-philosophical strictures of Richard Feynman. “Cocktail party philosophers,” he said in a lecture, think they can discover things about the world “by brainwork” rather than by experiment (“the test of all knowledge”). But in another lecture, he announced that the most pregnant hypothesis in all of science is that “all things are made of atoms.” Who first came up with this hypothesis? The ancient philosophers Leucippus and Democritus. And they didn’t come up with it by doing experiments.

Today the world of physics is in many ways conceptually unsettled. Will physicists ever find an interpretation of quantum mechanics that makes sense? Is “quantum entanglement” logically consistent with special relativity? Is string theory empirically meaningful? How are time and entropy related? Can the constants of physics be explained by appeal to an unobservable “multiverse”? Philosophers have in recent decades produced sophisticated and illuminating work on all these questions. It would be a pity if physicists were to ignore it.

And what about the oft-heard claim that philosophy, unlike science, makes no progress? As Bertrand Russell (himself no slouch at physics and mathematics) observed, philosophy aims at knowledge, and as soon as it obtains definite knowledge in a specific area, that area ceases to be called “philosophy.” And scientific progress gives philosophers more and more to do. Allow me to quote Nietzsche (although I know that will be considered by some to be in bad taste): “As the circle of science grows larger, it touches paradox at more places.” Physicists expand the circle, and philosophers help clear up the paradoxes. May both camps flourish.


by Jim Holt,the author of the forthcoming book “Why Does the World Exist? An Existential Detective Story.”


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