If the placebo was as powerful as Beecher said, and if doctors wanted to know whether their drugs actually worked, it was not sufficient simply to give patients the drugs and see whether they did better than patients who didn’t interact with the doctor at all. Instead, researchers needed to assume that the placebo effect was part of every drug effect, and that drugs could be said to work only to the extent that they worked better than placebos. An accurate measure of drug efficacy would require comparing the response of patients taking it with that of patients taking placebos; the drug effect could then be calculated by subtracting the placebo response from the overall response, much as a deli-counter worker subtracts the weight of the container to determine how much lobster salad you’re getting.

In the last half of the 1950s, this calculus gave rise to a new way to evaluate drugs: the double-blind, placebo-controlled clinical trial, in which neither patient nor clinician knew who was getting the active drug and who the placebo. In 1962, when the Food and Drug Administration began to require pharmaceutical companies to prove their new drugs were effective before they came to market, they increasingly turned to the new method; today, virtually every prospective new drug has to outperform placebos on two independent studies in order to gain F.D.A. approval.

Like Franklin’s commission, the F.D.A. had determined that the only way to sort out the real from the fake in medicine was to isolate the imagination. It also echoed the royal panel by taking note of the placebo effect only long enough to dismiss it, giving it a strange dual nature: It’s included in clinical trials because it is recognized as an important part of every treatment, but it is treated as if it were not important in itself. As a result, although virtually every clinical trial is a study of the placebo effect, it remains underexplored — an outcome that reflects the fact that there is no money in sugar pills and thus no industry interest in the topic as anything other than a hurdle it needs to overcome.

When Ted Kaptchuk was asked to give the opening keynote address at the conference in Leiden, he contemplated committing the gravest heresy imaginable: kicking off the inaugural gathering of the Society for Interdisciplinary Placebo Studies by declaring that there was no such thing as the placebo effect. When he broached this provocation in conversation with me not long before the conference, it became clear that his point harked directly back to Franklin: that the topic he and his colleagues studied was created by the scientific establishment, and only in order to exclude it — which means that they are always playing on hostile terrain. Science is “designed to get rid of the husks and find the kernels,” he told me. Much can be lost in the threshing — in particular, Kaptchuk sometimes worries, the rituals embedded in the doctor-patient encounter that he thinks are fundamental to the placebo effect, and that he believes embody an aspect of medicine that has disappeared as scientists and doctors pursue the course laid by Franklin’s commission. “Medical care is a moral act,” he says, in which a suffering person puts his or her fate in the hands of a trusted healer.

“I don’t love science,” Kaptchuk told me. “I want to know what heals people.” Science may not be the only way to understand illness and healing, but it is the established way. “That’s where the power is,” Kaptchuk says. That instinct is why he left his position as director of a pain clinic in 1990 to join Harvard — and it’s why he was delighted when, in 2010, he was contacted by Kathryn Hall, a molecular biologist. Here was someone with an interest in his topic who was also an expert in molecules, and who might serve as an emissary to help usher the placebo into the medical establishment.

Hall’s own journey into placebo studies began 15 years before her meeting with Kaptchuk, when she developed a bad case of carpal tunnel syndrome. Wearing a wrist brace didn’t help, and neither did over-the-counter drugs or the codeine her doctor prescribed. When a friend suggested she visit an acupuncturist, Hall balked at the idea of such an unscientific approach. But faced with the alternative, surgery, she decided to make an appointment. “I was there for maybe 10 minutes,” she recalls, “when she stuck a needle here” — Hall points to a spot on her forearm — “and this awful pain just shot through my arm.” But then the pain receded and her symptoms disappeared, as if they had been carried away on the tide. She received a few more treatments, during which the acupuncturist taught her how to manipulate a spot near her elbow if the pain recurred. Hall needed the fix from time to time, but the problem mostly just went away.