August 27, 2005

AS ANYONE remotely interested in science knows, 100 years ago Einstein wrote six papers that laid the groundwork for quantum mechanics and relativity, arguably the two most successful theories in history. To commemorate this, a coalition of physics groups has designated 2005 the World Year of Physics, with more than 400 events, including conferences, museum exhibits, concerts, webcasts, plays, poetry readings, a circus, a pie-eating contest and an Einstein lookalike competition.

Amid this hoopla, I feel compelled to deplore one aspect of Einstein’s legacy: the widespread belief that science and common sense are incompatible. In the pre-Einstein era, T.H. Huxley could define science as “nothing but trained and organized common sense”. But quantum mechanics and relativity shattered our common-sense notions about how the world works. The theories ask us to believe that an electron can exist in more than one place at the same time, and that space and time are not rigid but rubbery. Impossible. Yet these sense-defying propositions have withstood a century of tests.

Many scientists came to see common sense as an impediment to progress not only in physics, but also in other fields. “What, after all, have we to show for ... common sense,” the behaviourist B.F. Skinner asked, “or the insights gained through personal experience?” Elevating this outlook to the status of dogma, the biologist Lewis Wolpert declared: “I would almost contend that if something fits in with common sense it almost certainly isn’t science.”

Wolpert’s view is widely shared. When I invoke common sense to defend or — more often — criticize a theory, scientists invariably roll their eyes. Scientists’ contempt for common sense has two unfortunate implications. One is that preposterousness, far from being a problem for a theory, is a measure of its profundity; hence the appeal, perhaps, of dubious propositions like multiple-personality disorders and multiple-universe theories.

The other, more insidious implication is that only scientists are qualified to judge the work of other scientists. Needless to say, I reject that position, and not only because I’m a science journalist. I have found common sense — ordinary, non-specialized knowledge and judgment — to be indispensable for judging scientists’ pronouncements even, or especially, in the most esoteric fields.

For example, Einstein’s intellectual heirs have long been obsessed with finding a single “unified” theory that can embrace quantum mechanics, which accounts for electromagnetism and the nuclear forces, and general relativity, which describes gravity. The two theories employ very different mathematical languages and describe very different worlds, one lumpy and random and the other seamless and deterministic.

The leading candidate for a unified theory holds that reality stems from tiny strings or loops or membranes, or something wriggling in a hyperspace of 10 or 16 or 1,000 dimensions (the number depends on the variant of the theory, the day of the week, or the theorist’s zip code). A related set of “quantum gravity” theories postulates the existence of parallel universes — some mutant versions of our own, like Bizarro world in the Superman comics — existing beyond the borders of our little cosmos. “Infinite Earths in Parallel Universes Really Exist,” the normally sober Scientific American once hyperventilated on its cover.

All these theories are preposterous, but that’s not my problem with them. My problem is that no conceivable experiment can confirm the theories, as most proponents reluctantly acknowledge. The strings (or whatever) are too small to be discerned by any buildable instrument, the parallel universes too distant. Common sense persuades me these avenues of speculation will turn out to be dead ends.

Common sense — and historical perspective — makes me equally sceptical of grand unified theories of the human mind. We’re complex, variable, unpredictable creatures, whose personalities can be affected by a vast range of factors. I’m thus leery of hypotheses that trace some important aspect of our behaviour to a single cause.

Two examples: psychologist Frank Sulloway claimed that birth order has a profound, permanent impact on personality; firstborns tend to be conformists, whereas later-borns are “rebels”. And geneticist Dean Hamer argued that human spirituality stems from a specific snippet of DNA.

Although common sense biases me against these theories, I am still open to being persuaded on empirical grounds. But the evidence for both Sulloway’s birth-order theory and Hamer’s “God gene” is flimsy.

Over the past century, moreover, mind-science has been as faddish as teenage tastes in music, as one theory has yielded to another. Everything we think and do, scientists assured us, can be explained by the Oedipal complex, or conditioned reflexes, or evolutionary adaptations, or a gene in the X chromosome, or serotonin deficits in the amygdala. Given this turnover in paradigms, it’s sensible to doubt them all until the evidence for one becomes overwhelming.

While many scientists disparage common sense, artificial-intelligence researchers have discovered just how subtle and powerful an attribute it is. Researchers have programmed computers to perform certain tasks extremely well; computers can play championship chess, calculate a collision between two galaxies and juggle a million airline reservations. But computers fail miserably at simulating the ordinary, experience-based intelligence that helps ordinary humans get through ordinary days.

Yes, common sense alone can lead us astray, and some of science’s most profound insights into nature violate it; ultimately, scientific truth must be established on empirical grounds. Einstein once denigrated common sense as “the collection of prejudices acquired by age 18”, but retained a few prejudices of his own about how reality works.

His remark that “God does not play dice with the universe” reflected his stubborn insistence that specific causes yield specific effects; he could never fully accept the bizarre implication of quantum mechanics that at small scales reality dissolves into a cloud of probabilities.

So far, Einstein seems to be wrong about God’s aversion to games of chance, but he was right not to abandon his common-sense intuitions about reality. In those many instances when evidence is tentative, we should not be embarrassed to call on common sense for guidance. — Dawn/The Guardian News Service

The writer oversees the science writing programme at the Stevens Institute of Technology

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