What the 1784 Report Invented Without Meaning To

The commission concluded that no evidence supported the existence of a magnetic fluid and that the effects observed were produced by imagination, by imitation among patients treated in groups, and by touch. Read now, the report is remarkable less for its verdict than for its method, and it is routinely cited in the history of clinical trials as an early and unusually clean use of two techniques that would not be named for another century and a half. The first is blinding: the subject was prevented from knowing whether the treatment was being administered, which is the only way to separate a treatment from the belief that it is being given. The second is a genuine control condition, since sham magnetisation was applied and compared against the real thing rather than merely reasoned about.

Franklin himself drew a conclusion the report only implies, remarking that some of the cures were real even if the theory was nonsense, and wondering in correspondence whether the imagination might be turned to account deliberately. That is close to the modern research question about placebo response, arrived at two centuries early and then dropped. The report also had a political edge, since Mesmer's clientele overlapped with fashionable Paris, and its authors were aware they were puncturing a craze as well as a theory.