Originally published 15 February 1993
“Darling, you and I know the reason why
The summer sky is blue,
And we know why birds in the trees
Sing melodies too.”
Songwriter Meredith Willson, who wrote these lyrics, thought he knew why the sky is blue and birds sing. Nobel-prizewinning physicist Steven Weinberg thinks he knows too.
The sky is blue because air molecules scatter short-wavelength blue light more effectively than other colors of the spectrum. The singing of birds is explained by molecular DNA. At a deeper level, all of this molecular stuff can be reduced to quantum physics. Behind quantum physics are a few primal laws we have just begun to glimpse.
In fact, says Weinberg, everything will ultimately be explained by a “final theory” of stunning simplicity. It will be a mathematical theory, related to present-day theories of elementary particle physics. It will be the glittering point where all lines of explanation converge.
This is the theme of Weinberg’s new book, Dreams of a Final Theory. It is a wonderful book. It is a provocative book. In the recent spate of books by Nobel-laureate physicists, it is the best.
Weinberg’s philosophy is called reductionism. He is not the first, nor will he be the last, to embrace it. Biology is chemistry, says Weinberg, chemistry is physics, physics is elementary particle physics, and elementary particle physics is the bottom of the ladder.
He writes: “Reductionism is not a guideline for research programs, but an attitude toward nature itself. It is nothing more or less than the perception that scientific principles are the way they are because of deeper scientific principles (and, in some cases, historical accidents) and that all these principles can be traced to one simple set of connected laws.”
Weinberg’s brand of reductionism has a nasty, inhuman odor about it. The idea that we are just a bunch of elementary particles bouncing about in the void is chilling and impersonal. If there is a meaning to the world, we would like it to be something more than whatever it is that elementary particle physicists do.
Something more akin to blue summer skies and bird songs and you and I.
Even Weinberg waffles, as well he should. He calls his chapter on all of this “Two Cheers for Reductionism.” He admits “historical accidents” into his definition. He allows that the present pre-eminence of elementary particle physics may be temporary.
But at heart he’s a true believer. The reductionist world view may be chilling and impersonal, but he insists it must be accepted, not because we like it, but because that’s the way the world works. He believes elementary particle physicists have every right to claim their discipline is more fundamental than other branches of science, because it is. Period.
And he makes a compelling case. But when all is said and done, I suspect that Meredith Willson knew as much as Weinberg does about why the sky is blue and why birds sing.
Reductionism is not science. It’s not even philosophy. It’s religion, pure and simple, a matter of faith. And the person who believes that love, music, blue skies, and the melodies of birds cannot, even in principle, be reduced to elementary particle physics has as much or as little basis for belief as the reductionist.
I would turn Weinberg’s definition on its ear. Reductionism has been a successful guideline for research programs, but as an attitude toward nature it’s a flop.
Sure, we have learned a lot about the world by breaking things down into their parts, but who knows what we might learn with more holistic approaches. Reductionism has worked well so far is because that’s the only kind of science we have been able to handle mathematically. With the advent of high-speed supercomputers, holistic ways of explaining things might emerge which are equally successful. I’m not talking about New Age “holism” but solid science. Certain theories called cellular automata and chaos provide sketchy outlines of the future.
By the end of the next century we might look back on reductionist theories of physics as hopelessly out-of-date.
And if we do, we shall certainly remark upon the hubris of 20th century physicists who thought a final theory was within our grasp.
A little hubris is not a bad thing for a scientist. Anyone who would attempt to explain the universe must possess some measure of arrogance. The important thing is to not let hubris get out of control. Here’s my scientific heresy, which like Weinberg’s is a matter of faith: No theory conceived by the human mind will ever be final. The universe is vast, marvelous, and deep beyond our wildest imagining — its horizons will forever recede before our advance. All dreams of finality are futile. Period.
You and I have only the vaguest idea why the summer sky is blue, and we have only the vaguest idea why birds in the trees sing melodies too. But I’ll concede this: Thanks to reductionist theories of science, we know a helluva lot more about these things than we used to.
