Marrying your dentist, as I did, means learning all sorts of things you never imagined you’d know. Some of them are even useful. Smoking, for instance, will make your teeth fall out, and raisins can be harder on the old choppers than chocolates. But the biggest lesson has to do with technology. What I’ve learned about this from being around my wife is that there are no Luddites with toothaches.

The Luddites, you’ll recall, were disaffected craftsmen who destroyed newfangled textile machinery in England in the early 19th century. Today lots of people fear technology, or at least new technology, and a certain amount of Luddism is probably inevitable in a time of rapid change. But what’s striking, as people cope with all of this, is how irrational we can be when confronted with everyday technologies we don’t understand. Los Angeles, where my wife practiced dentistry, is a showcase for the phenomenon of “selective Luddism”: a big, sophisticated city that hasn’t fluoridated its water. My wife’s patients there included plenty of people who were open to almost any new idea, yet were deeply suspicious of modern medicine and technology-except, of course, when they had a toothache, at which point they were happy to embrace any substance or technology that brought them relief. I remember much wariness about silver fillings, but hardly a peep about lidocaine.

Some of this is understandable. With its sunshine and smog, caressing breezes and crime, there is a quality of paradise lost about Los Angeles that can make anyone leery of progress. Yet human responses to civilization’s discontents are frustratingly inconsistent. Our friends in L.A. wear machine-made clothing and drive cutting-edge cars through a web of sophisticated traffic signals, architecture and engineering to reach health-food stores where they escape modern farming technologies by “buying organic.”

When my wife was carrying our twins, we encountered pregnant women who insisted on natural childbirth-in a high-tech medical center, of course. I confess to being puzzled. Advocates of natural childbirth don’t walk barefoot to the hospital, after all, and they bring the new baby home to a house with indoor plumbing and central heat. They don’t stop buying shampoo or sending e-mail, either, and they have countless sonograms en route to delivery. So why the desire to experience “natural” childbirth?

I think “experience” is the operative concept here, backed by a general desire to be free of what we perceive as the dangers of technology at such a sensitive moment. We remember at such times that medical science brought the world thalidomide, but we remember also how useful blood tests, amniocentesis and the like can be in helping safeguard mothers and fetuses. So we’re torn. To borrow an adage from Madison Avenue, we think half of all the money spent on technology is wasted. The question is, which half?

The classic example, of course, is flying. You are probably safer on a major U.S. airline than in your bathtub, yet my mother-in-law (who smokes cigarettes) is still somewhat afraid to fly. Who understands, after all, what keeps airplanes aloft? Who was this guy Bernoulli anyway? Microwave ovens, despite their well-established harmlessness, are also a focal point for outbreaks of selective Luddism. A friend in Santa Monica won’t own one, even though she uses a computer every day, commutes to work by car, and casually flies coast to coast.

What accounts for all this selective Luddism? My friend’s phobia points to a possible explanation, which is that people’s willingness to embrace a new technology is in inverse proportion to its invisibility. Sensitized by stories of the harm caused by chemicals and radiation, people are nervous about microwave ovens, cellular telephones and other mysterious electronic devices. Thus food irradiation, which would save many lives annually, remains largely taboo. That so many of these modern technologies are simply beyond the average person’s understanding only enhances people’s fears. (A kind of technological grandfather clause seems to exempt television and radio transmissions, which are also invisible-perhaps because they became commonplace in the days when people still thought radiation was fun. Remember, there was a time when children routinely put their feet into X-ray machines…in shoe stores.)

Yet safety can’t be the main issue. The automobile, for instance, is a very risky technology indeed. Each year auto accidents kill more than 40,000 Americans and injure 3.5 million others. Not only that, the internal combustion engine gives off air pollution that kills thousands and plays a major role in the accelerating warming of the planet. Driving everywhere also makes people fat, which further contributes to health problems. Yet my mother-in-law doesn’t hesitate to get into her Volvo, as long as she doesn’t have to drive it to the airport to catch a plane.

The case of the car suggests a second possible explanation for selective Luddism: If a technology offers irresistible personal benefits, we will embrace it regardless of the risks. In this sense, the selectivity is rational, since people have decided that the freedom, time-savings and other advantages of auto ownership outweigh the many disadvantages of driving.

But what about high-tension wires? Universal electrification brings very tangible benefits, after all. Here, however, the Problem of the Commons arises, except in reverse. Instead of individual benefit and socialized cost, we have socialized benefit and at least the perception of individual cost. Therefore, we reject the perceived risk of living near high-tension wires even when we understand that somebody’s got to do it. Selective Luddism makes at least a superficial kind of sense here too.

Nevertheless, selective Luddism is not the result of any sophisticated calculus of risks, as is evident at your neighborhood McDonald’s. Modern fast food establishments sell food that is unmistakably a product of technology. It’s also usually filled with fat, salt and calories, which doesn’t stop millions of Americans from gorging on it daily. It’s hard to believe people think the benefits of greasy gray hamburgers outweigh the risk of heart disease. But the threat of fast food is visible, the technology is easy to understand, and the likelihood of harm is far in the future. This points to yet another possible explanatory principle of selective Luddism, which is that people seem to fear a low probability of immediate harm much more than a high probability of harm some day in the hazy and far-off future. That’s why people still buy cigarettes.

The selectivity of Luddism also seems to vary with social class. In most of the country, for instance, vinyl windows and siding make sense, and because of their affordability are embraced by people who don’t have a lot of money. On the other hand, these products are regarded by the well-to-do as hopelessly tacky-perhaps, as the sociologist Thorstein Veblen suggested with his theory of conspicuous consumption, precisely because they are so practical and cheap. Wood, which is torn from the forest and requires constant care on a house, remains much more socially acceptable among those who look down on the working class.

Class-based aesthetics, in fact, seems to play a role in many of the decisions people make about technology. Perhaps this is why professional ballerinas shun high-tech ballet slippers in favor of anachronistic pointe shoes that cost $50 a pair and can wear out after a single performance. Edward Tenner, a student of technology whose book Why Things Bite Back could give ammunition to Luddites who fail to read it carefully, points to another such case: the rise of the high-tech bowling ball. It seems that technology in this field is so advanced that a new generation of balls is sharply changing the nature of the game, making it much more “strike intensive,” in Tenner’s words. Purists are appalled, contending that the skill and strategy involved in nailing a difficult split are falling by the wayside.

What to do if you detect the symptoms of selective Luddism in your household? Relax. In the end, selective Luddism makes a certain sense, for who can foretell the impact of a new technology? Who imagined, for instance, that air conditioning would transform Houston into one of the largest cities in North America? That the birth control pill would fuel the sexual revolution? That computers would facilitate adjustable-rate mortgages? Or that television would become the predominant cultural medium of our age? Only a clairvoyant. The rest of us, swept along on the tides of history, must take technologies as they come.

Besides, people have always adopted new ideas at different rates. After citrus was found to prevent scurvy, years went by before the Royal Navy adopted the measures that led the English to be called Limeys. Sometimes the problem is that it takes a while for people to figure out how a new technology might best be used. The full effect of electrical power on factory productivity, for example, took years to manifest itself.

And some new technologies-personal computers, for instance-were probably adopted too soon, rather than too late. Billions have been spent on computer technology, but there is serious debate over whether any productivity gains have resulted. It’s doubtful, though, that computers would get as good as they are going to be without first being ornery and difficult to use.

So maybe what I’m calling selective Luddism is really just people’s natural need to grope their way into tomorrow. Very, very few of us, after all, wish to abandon technology altogether, much as we may lament the various technological developments that have changed our lives. I have noticed that admirers of primitive tribal cultures make no effort, when they get home, to have the telephone taken out, and I am pleased to note that even hardened reactionaries, like the narrator of John Lanchester’s novel The Debt to Pleasure, usually make an exception for dentistry as an unalloyed good resulting from the modern age.

In a sense, we’re all selective Luddites, and true enemies of technology stand out only because of the depth and arbitrariness of their convictions, which are closer to religion than to reason. Even the Unabomber didn’t hate all technologies. Explosives, for instance, seemed to suit his Luddite mentality just fine.