Another gray matter

IT’S hard to know what to make of a book about what scientists believe but cannot prove. Proof, after all, is what scientists do. Proof is what distinguishes science from belief.

Of course, proof is not always what it’s cracked up to be. As mathematician Keith Devlin points out in “What We Believe but Cannot Prove,” a book of essays edited by John Brockman, some of Euclid’s proofs turned out centuries later to be incorrect. “So even in the case of a ten-line proof in geometry,” Devlin writes, “it can be hard to tell right from wrong.”

As for belief, it’s true that scientists rely often enough on hunches, intuition, even guesswork. As Mark Twain famously quipped: “There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.”

So I was prepared to give Brockman’s collection of ruminations on the subject of proof by “the preeminent intellectuals of our time” the benefit of the doubt. I was even prepared to overlook the rather silly puffery (“the 109 most brilliant minds!”). Although many of the authors are first-rate scientists and writers, others as surely are not.

One of the special pleasures of science is that it forces us to think hard about what we mean by terms like “proof” and “belief” -- as well as “truth,” “cause,” “understanding” and even “reality.” Which is ultimately why this book is so annoying. For the most part, it reads like a bunch of blog entries -- sound bites as short as a sentence that either state the obvious or cut off just as things get interesting, random bursts of intellectualizing designed for compulsive channel surfers.

Fans (and I count myself among them) of such contributors as Jared Diamond, Steven Pinker, Sir Martin Rees, Freeman Dyson, Daniel Dennett and Howard Gardner would be better off sticking to their wonderful books.

The problem here isn’t the brevity. Many a scientist (the late Lewis Thomas, for one) conveyed a universe of meaning in a page or two of lyric prose. The worst of these entries seem so tossed off they could almost be taken for a snatch of overheard cellphone conversation. And in a sense, bits of conversation is exactly what they are. Every year, Brockman -- a literary agent primarily for scientists -- invites several hundred people (many of them clients) to respond to a question that comes to him (or one of his contributors) “in the middle of the night.” He publishes them on his website, www.edge.org.

The essays worth reading take pains to put beliefs in context: Psychologist Irene Pepperberg studies how gray parrots talk and think (compared with apes, marine mammals and children). She believes birds are the best model for understanding human language. But before making her argument, she offers a highly informative backgrounder on bird song. So, by the time she proposes that the “missing link” between learned and unlearned vocalizing may be found in a recently discovered flycatcher that learns its songs, you’re ready to go along.

But most are neither as original, entertaining or even thought-out. Instead, for example, we are told: People lie and that leads to bad things. Not everything is understandable. Evolution is real. We are not alone.

Some entries are rebuttals to ideas that aren’t even argued in the book: “String theory is a futile exercise.” Some boil down to: “I believe in me.”

The most interesting responses confront notions of proof and belief directly. Experimental physicist Maria Spiropulu turns the ambiguous notion of proof into the more easily definable “clarity” -- then changes belief into “assessment,” either theoretical or commonsense. Even so, her answer remains: “Nothing.” “If you believe something, then you don’t need proof of it, and if you have proof, you don’t need to believe.”

Theoretical physicist Leonard Susskind uses a parable to explain that all proof is ultimately based on probability. He can’t prove that a coin flipped a million times won’t come up consistently heads. But he’d bet his life, soul (and even his salary) on it. Mathematician Devlin admits that he believes Andrew Wiles’ 1994 proof of Fermat’s last theorem only because “experts in that branch of mathematics tell me they do.”

This isn’t to say there’s no objective truth; it means only that our brains are no match for Nature’s inherent complexity.

One especially poetic and thought-provoking essay confronts both belief in the afterlife and prospects for proof of its existence. Experimental psychologist Jesse Bering calls such beliefs a flaw in our thinking resulting from “blemished psychological hardware.” Of course, he admits, the question of “what it’s like” to be dead can never be resolved. “The proof isn’t in the empirical pudding,” he says. “It can’t be. It’s death we’re talking about, after all.”

Biologist Robert M. Sapolsky doesn’t believe in God, he says, even though he can’t prove God doesn’t exist. If someone else proved it, though, that would be fine with him. “I don’t need to believe there is a God in order to berate him.”

Whether or not we believe proof or prove belief, understanding belief itself becomes essential in a time when so many people in the world are ardent believers -- some of whom act on their beliefs with no small consequence. “What does it mean, at the level of the brain, to believe that a proposition is true?” asks author and neuroscientist Sam Harris. Harris believes the same neural process is involved in sensing beauty; truth and beauty, in other words, are linked by the brain’s “reward-related circuitry.”

Curiously, only one respondent -- psychologist David Buss -- professes belief in true love. *