February 14, 2005

Truth, Incompleteness and the Gödelian Way

John Patrick Naughton Rebecca Goldstein's new book is about the mathematician Kurt Gödel.

elativity. Incompleteness. Uncertainty.

Is there a more powerful modern Trinity? These reigning deities proclaim humanity's inability to thoroughly explain the world. They have been the touchstones of modernity, their presence an unwelcome burden at first, and later, in the name of postmodernism, welcome company.

Their rule has also been affirmed by their once-sworn enemy: science. Three major discoveries in the 20th century even took on their names. Albert Einstein's famous Theory (Relativity), Kurt Gödel's famous Theorem (Incompleteness) and Werner Heisenberg's famous Principle (Uncertainty) declared that, henceforth, even science would be postmodern.

Or so it has seemed. But as Rebecca Goldstein points out in her elegant new book, "Incompleteness: The Proof and Paradox of Kurt Gödel" (Atlas Books; Norton), of these three figures, only Heisenberg might have agreed with this characterization.

His uncertainty principle specified the inability to be too exact about small particles. "The idea of an objective real world whose smallest parts exist objectively," he wrote, "is impossible." Oddly, his allegiance to an absolute state, Nazi Germany, remained unquestioned even as his belief in absolute knowledge was quashed.

Einstein and Gödel had precisely the opposite perspective. Both fled the Nazis, both ended up in Princeton, N.J., at the Institute for Advanced Study, and both objected to notions of relativism and incompleteness outside their work. They fled the politically absolute, but believed in its scientific possibility.

And therein lies Ms. Goldstein's tale. From the late 1930's until Einstein's death in 1955, Einstein and Gödel, the physicist and the mathematician, would take long walks, finding companionship in each other's ideas. Late in his life, in fact, Einstein said he would go to his office just to have the "privilege" of walking with Gödel. What was their common ground? In Ms. Goldstein's interpretation, they both felt marginalized, "disaffected and dismissed in profoundly similar ways." Both thought that their work was being invoked to support unacceptable positions.

Einstein's convictions are fairly well known. He objected to quantum physics and its probabilistic clouds. God, he famously asserted, does not play dice. Also, he believed, not everything depends on the perspective of the observer. Relativity doesn't imply relativism.

The conservative beliefs of an aging revolutionary? Perhaps, but Einstein really was a kind of Platonist: He paid tribute to science's liberating ability to understand what he called the "extra-personal world."

And Gödel? Most lay readers probably know of him from Douglas R. Hofstadter's playful best-seller "Gödel, Escher, Bach," a book that is more about the powers of self-referentiality than about the limits of knowledge. But the latter is the more standard association. "If you have heard of him," Ms. Goldstein writes, perhaps too cautiously, "then there is a good chance that, through no fault of your own, you associate him with the sorts of ideas - subversively hostile to the enterprises of rationality, objectivity, truth - that he not only vehemently rejected but thought he had conclusively, mathematically, discredited."

Ms. Goldstein's interpretation differs in some respects from that of another recent book about Gödel, "A World Without Time: The Forgotten Legacy of Gödel and Einstein" by Palle Yourgrau (Basic), which sees him as more of an iconoclastic visionary. But in both he is portrayed as someone widely misunderstood, with good reason perhaps, given his work's difficulty.

Before Gödel's incompleteness theorem was published in 1931, it was believed that not only was everything proven by mathematics true, but also that within its conceptual universe everything true could be proven. Mathematics is thus complete: nothing true is beyond its reach. Gödel shattered that dream. He showed that there were true statements in certain mathematical systems that could not be proven. And he did this with astonishing sleight of hand, producing a mathematical assertion that was both true and unprovable.

It is difficult to overstate the impact of his theorem and the possibilities that opened up from Gödel's extraordinary methods, in which he discovered a way for mathematics to talk about itself. (Ms. Goldstein compares it to a painting that could also explain the principles of aesthetics.)

The theorem has generally been understood negatively because it asserts that there are limits to mathematics' powers. It shows that certain formal systems cannot accomplish what their creators hoped.

But what if the theorem is interpreted to reveal something positive: not proving a limitation but disclosing a possibility? Instead of "You can't prove everything," it would say: "This is what can be done: you can discover other kinds of truths. They may be beyond your mathematical formalisms, but they are nevertheless indubitable."

In this, Gödel was elevating the nature of the world, rather than celebrating powers of the mind. There were indeed timeless truths. The mind would discover them not by following the futile methodologies of formal systems, but by taking astonishing leaps, making unusual connections, revealing hidden meanings.

Like Einstein, Gödel was, Ms. Goldstein suggests, a Platonist.

Of course, those leaps and connections could go awry. Gödel was an intermittent paranoiac, whose twisted visions often left his colleagues in dismay. He spent his later years working on a proof of the existence of God. He even died in the grip of a perverse esotericism. He feared eating, imagined elaborate plots, and literally wasted away. At his death in 1978, he weighed 65 pounds.

But he was no postmodernist. Late in his life Gödel said of mathematics: "It is given to us in its entirety and does not change, unlike the Milky Way. That part of it of which we have a perfect view seems beautiful, suggesting harmony." That beauty, he proposed, would be mirrored by the world itself. These are not exactly the views of an acolyte devoted to Relativity, Incompleteness and Uncertainty. And Einstein was his fellow dissenter.

The Connections column will appear every other Monday.