Thirteen years after the legendary confrontation over the theory of evolution between Bishop Samuel Wilberforce ("Soapy Sam") and Thomas Henry Huxley ("Darwin's bulldog"), Wilberforce died in 1873 in an equestrian fall. Huxley quipped to physicist John Tyndall, "For once, reality and his brain came into contact and the result was fatal."

When it comes to such basic forces as gravity and such fundamental phenomena as falling, our intuitive sense of how the physical world works--our folk physics--is reasonably sound. Thus, we appreciate Huxley's wry comment and note that even children get the humor of cartoon physics, where, for example, a character running off a cliff does not fall until he realizes that he has left terra firma.

But much of physics is counterintuitive, as is the case in many other disciplines, and before the rise of modern science we had only our folk intuitions to guide us. Folk astronomy, for example, told us that the world is flat, celestial bodies revolve around the earth, and the planets are wandering gods who determine our future. Folk biology intuited an lan vital flowing through all living things, which in their functional design were believed to have been created ex nihilo by an intelligent designer. Folk psychology compelled us to search for the homunculus in the brain--a ghost in the machine--a mind somehow disconnected from the brain. Folk economics caused us to disdain excessive wealth, label usury a sin and mistrust the invisible hand of the market.

Folk science gets it wrong because we evolved in a radically different environment.

The reason folk science so often gets it wrong is that we evolved in an environment radically different from the one in which we now live. Our senses are geared for perceiving objects of middling size--between, say, ants and mountains--not bacteria, molecules and atoms on one end of the scale and stars and galaxies on the other end. We live a scant three score and 10 years, far too short a time to witness evolution, continental drift or long-term environmental changes.

Causal inference in folk science is equally untrustworthy. We correctly surmise designed objects, such as stone tools, to be the product of an intelligent designer and thus naturally assume that all functional objects, such as eyes, must have also been intelligently designed. Lacking a cogent theory of how neural activity gives rise to consciousness, we imagine mental spirits floating within our heads. We lived in small bands of roaming hunter-gatherers that accumulated little wealth and had no experience of free markets and economic growth.

Folk science leads us to trust anecdotes as data, such as illnesses being cured by assorted nostrums based solely on single-case examples. Equally powerful are anecdotes involving preternatural beings, compelling us to make causal inferences linking these nonmaterial entities to all manner of material events, illness being the most personal. Because people often re-cover from sickness naturally, whatever was done just before recovery receives the -credit, prayer being the most common.

In this latter case, we have a recent scientific analysis of this ancient folk science supposition. The April issue of the American Heart Journal published a comprehensive study directed by Harvard Medical School cardiologist Herbert Benson on the effects of intercessory prayer on the health and recovery of patients undergoing coronary bypass surgery. The 1,802 patients were divided into three groups, two of which were prayed for by members of three religious congregations. Prayers began the night before the surgery and continued daily for two weeks after. Half the prayer recipients were told that they were being prayed for, whereas the other half were told that they might or might not receive prayers. Results showed that prayer itself had no statistically significant effect on recovery. Case closed.

Of course, people will continue praying for their ailing loved ones, and by chance some of them will recover, and our folk science brains will find meaning in these random patterns. But for us to discriminate true causal inferences from false, real science trumps folk science.