Have you noticed the lengthy New York Times magazine article on the always fascinating topic of the placebo effect? It's really good, and I particularly liked the explanation of how it was more or less discovered as a thing when Benjamin Franklin was involved in French ordered investigations as to how Mesmerism seemed to be effective, for some.
I will extract some of that:
In a way, the placebo effect owes its poor reputation to the same man who cast aspersions on going to bed late and sleeping in. Benjamin Franklin was, in 1784, the ambassador of the fledgling United States to King Louis XVI’s court. Also in Paris at the time was a Viennese physician named Franz Anton Mesmer. Mesmer fled Vienna a few years earlier when the local medical establishment determined that his claim to have cured a young woman’s blindness by putting her into a trance was false, and that, even worse, there was something unseemly about his relationship with her. By the time he arrived in Paris and hung out his shingle, Mesmer had acquired what he lacked in Vienna: a theory to account for his ability to use trance states to heal people. There was, he claimed, a force pervading the universe called animal magnetism that could cause illness when perturbed. Conveniently enough for Mesmer, the magnetism could be perceived and de-perturbed only by him and people he had trained.
Mesmer’s method was strange, even in a day when doctors routinely prescribed bloodletting and poison to cure the common cold. A group of people complaining of maladies like fatigue, numbness, paralysis and chronic pain would gather in his office, take seats around an oak cask filled with water and grab on to metal rods immersed in the water. Mesmer would alternately chant, play a glass harmonium and wave his hands at the afflicted patients, who would twitch and cry out and sometimes even lose consciousness, whereupon they would be carried to a recovery room. Enough people reported good results that patients were continually lined up at Mesmer’s door waiting for the next session.
It was the kind of success likely to arouse envy among doctors, but more was at stake than professional turf. Mesmer’s claim that a force existed that could only be perceived and manipulated by the elect few was a direct challenge to an idea central to the Enlightenment: that the truth could be determined by anyone with senses informed by skepticism, that Scripture could be supplanted by facts and priests by a democracy of people who possessed them. So, when the complaints about Mesmer came to Louis, it was to the scientists that the king — at pains to show himself an enlightened man — turned. He appointed, among others, Lavoisier the chemist, Bailly the astronomer and Guillotin the physician to investigate Mesmer’s claims, and he installed Franklin at the head of their commission.
To the Franklin commission, the question wasn’t whether Mesmer was a fraud and his patients were dupes. Everyone could be acting in good faith, but belief alone did not prove that the magnetism was at work. To settle this question, they designed a series of trials that ruled out possible causes of the observed effects other than animal magnetism. The most likely confounding variable, they thought, was some faculty of mind that made people behave as they did under Mesmer’s ministrations. To rule this out, the panel settled upon a simple method: a blindfold. Over a period of a few months, they ran a series of experiments that tested whether people experienced the effects of animal magnetism even when they couldn’t see.Go read it all, as it goes onto to talk about recent research indicating a molecular reason why placebos seem to work so well on some people, at least.