Now, though, that taboo is fading, and Moseley and Wray are not the only ones arguing that new surgical techniques, like new medicines, ought to be tested with placebo controls. Doctors investigating a new technique for treating Parkinson's disease, for example, incorporated a placebo control group -- patients who had holes drilled in their skulls to simulate the real procedure, in which fetal cells are implanted in the brain -- into a widely publicized study released last April. The study showed a significant placebo effect, though the motor ability of the patients who actually got the fetal implants improved even more. ''This is just the beginning,'' Dr. C. Warren Olanow, chairman of neurology at Mount Sinai School of Medicine, told Time magazine. ''Tomorrow, if you have a new procedure, you will have to do a double-blind placebo trial.''

Some doctors argue, with reason, that the new enthusiasm for placebo surgery is driven by hospital bean counters and insurers who want hard evidence that an expensive procedure works before they'll pay for it. And yet, with all due respect for medical economics, that can't be the only explanation. If placebo surgery makes sense, it makes sense because of the growing body of evidence for the strength of the placebo effect in general. Maybe pretend operations are just the most sensational proof of a diffuse phenomenon that has never quite been explained, but that, as the historian of science Anne Harrington has written, continues to ''haunt our house of biomedical objectivity.''

The truth is that the placebo effect is huge -- anywhere between 35 and 75 percent of patients benefit from taking a dummy pill in studies of new drugs -- so huge, in fact, that it should probably be put to conscious use in clinical practice, even if we do not entirely understand how it works. For centuries, Western medicine consisted of almost nothing but the placebo effect. The patient who got better after a bleeding -- or a dose of fox lung, wood lice, tartar emetic or any of the other charming staples of the 19th-century pharmacopoeia -- got better either in spite of them or because of their symbolic value. Such patients believed in the cure and in the authority of the bewigged gentlemen administering it, and the belief gave them hope and the hope helped make them well. There were exceptions -- remedies, like quinine for malaria, the vaccine for smallpox and morphine for pain relief, that actually worked. But generally speaking, if all the drugs of the day ''could be sunk to the bottom of the sea,'' as Oliver Wendell Holmes observed in 1860, ''it would be all the better for mankind -- and all the worse for the fishes.''

In the postwar era, with the triumph of the biomedical model and the proliferation of drugs and techniques that did successfully extend life, many doctors would just as soon have forgotten about the placebo effect altogether. They now had proven remedies and methods: antibiotics for infection; dazzling surgical techniques like heart and liver transplantation; sophisticated diagnostic tools like magnetic resonance imaging. In fact, medical science has improved so much and so fast in the last 40 years that it is easy, perhaps, for doctors to neglect the part of medicine that is not science at all. The ready and lavish display of sympathy, the laying on of hands, the projection of a slightly mystical authority -- these are now more often the province of alternative medical practitioners, who have no compunction about manipulating them. In a recent edition of a British medical journal, a general practitioner wondered whether he ought to give an 86-year-old patient a pharmacologically useless ''tonic'' she had requested in fond remembrance of the ones her old doctor had given her. ''I don't use tonics routinely anymore,'' he wrote, ''but perhaps I should: they are pharmacologically pretty harmless and cheap to boot. Homeopathy, herbs and talkative middle-aged ladies who squeeze your feet have replaced them, but because I do not offer these alternative medicines, my patients go elsewhere for their magic, hope and comfort.''

But what if doctors firmly in the fold of evidence-based medicine were not so circumspect about offering magic, hope and comfort? What if they did resort more often to tonics or their equivalent -- to the old-fashioned squeezing of the hand and the slightly unrealistic imparting of hope that is now frowned upon as a bit too authoritarian and paternalistic? What if they started thinking of placebos as a way of bridging the gap between the magnificent but sometimes cold efficiency of modern American medicine and the unproven but evidently comforting remedies prescribed by homeopaths and herbalists? After all, more and more people seem to be drawn to alternative medical therapies -- half of all Americans say they have tried them -- despite a distinct lack of empirical proof for their effectiveness. Yet people may actually harm themselves if they down the latest untested herbal panacea, while if they take an inert substance (or get a cheering speech) given by a conventional physician, they will do no worse and they stand a good statistical chance of doing better. There is something to be said, surely, for a little benign deception.

Though a few doctors are starting to argue for a more conscious use of the placebo effect, even for the deliberate prescribing of dummy pills, this is not an easy case to make. Placebos have long slunk around with a reputation as nuisances -- necessary, but annoying. Most of us know them as the pharmacologically inert drugs given to some of the subjects in so-called double-blind studies of new drugs, in which neither the subjects nor the researcher know who is getting what. If as many subjects improve by taking the placebo as do by taking the active drug, then the active drug is thought to be a bust. It happens all the time, even to highly touted new medications. Last summer, the share price of a British biotech company called Peptide Therapeutics dropped 33 percent after it revealed that its new allergy vaccine was only as effective as a placebo. During the trials on food-allergy patients, a company spokesman had reported delightedly, 75 percent had improved to the point where they could tolerate foods they'd never been able to before. But when the control group data came in, so, awkwardly enough, had 75 percent of the subjects taking inert tablets. Last year, the pharmaceutical company Merck announced that it was halting development of MK-869, a new antidepressant it had been promoting for months as a blockbuster drug on the scale of Prozac. Alas, the dummy pills worked just as well. And in a recent study on VEGF, a genetically engineered heart drug announced with much fanfare by its manufacturer, Genentech, the placebo actually performed better. Two months after their treatments, patients who had gotten low doses of VEGF could walk 26 seconds longer on a treadmill, those who had gotten high doses could walk 32 seconds longer and those who had gotten a placebo could walk -- go figure -- 42 seconds longer.

Of course, patients are often far from pleased to hear how well their placebos have worked. ''Once we did a PMS study where we treated people for a month with placebo and then told people who'd responded what they'd been on,'' says Karen Weihs, a clinical psychiatrist at George Washington University. ''And as it turns out, it's a very difficult thing to confront somebody with. Some people feel insulted, or silly. You're telling them it's all in their mind. We try to frame it positively -- your symptoms aren't so severe that you need medication; your mind has other ways of making you feel better. But that doesn't always help.''