(This is the fifth in a series of posts on eponyms.)
These days when we speak of being mesmerized by something, we may not realize we are referencing the theories and practices of Franz Anton Mesmer (1734-1815), a German physician. (While being mesmerized is eponymous, most of its synonyms are metaphorical: if we are captivated or enthralled by something, we are a slave to it; if we are spellbound by it, it has cast a spell over us.) Believing that illness was the result of a misalignment of magnetic forces in the human body, Mesmer initially engaged in curing his patients by giving them high doses of iron and then passing magnets over their bodies. When Mesmer came to realize that the success of his treatments arose from his own magnetic force, the magnets were discarded, with treatment involving Mesmer’s passing his empty hands above a patient’s body. Mesmer must have been a very convincing physician with malleable patients; apparently he managed to put his patients into a trance-like state, from which they emerged improved—at least often enough. Although Mesmer was discredited by the medical communities of Vienna and Paris, mesmerism and/or “animal magnetism” (the term used by Mesmer) gained in popularity in Germany, Russia, England, America, and elsewhere. (For greater detail / some of “the rest of the story,” see these accounts:   .)
Over time, mesmerism has lost some of the strength of its connection with Mesmer and animal magnetism. The word is now roughly synonymous with hypnosis, as reflected in Mesmerism being given as a Relative Index term at 154.7 Hypnotism. (DDC 20 included a discontinuation of works on mesmerism from 154.72 Animal magnetism to 154.7 Hypnotism.) When classifying works that use the term mesmerism, one should be careful to discern whether it is meant in its historical sense, specific to Franz Anton Mesmer and animal magnetism, or in its more contemporaneous and general sense.
Two see references at 154.7 are also relevant to us: one tells us that psychic aspects of hypnotism are classed in 133.89 [Psychic phenomena] Animal magnetism, hypnosis, extrasensory perception of animals, aura; the other tells us that medical applications of hypnotism are classed in 615.8512 [Psychological and activity therapies] Hypnotherapy. Consequently, Manuel de magnétisme: petit manuel de magnétisme et médecine homéopathique [Handbook of magnetism: small handbook of magnetism and homeopathic medicine] is classed in 615.8512.
And what about the comprehensive biography number for Mesmer? It is easy to read about Mesmer’s theories and consider him a bit of a charlatan, but this is unfair. Even if his explanations now strike us as misguided, his curative successes were apparently real. That is, as a theorist, we might consider his most noted contributions to be a better fit in 133.89 than in 615.8512, but as a practitioner, he’s a good fit in 615.8512. The Manual at T1—092 Biography instructs us: “If the person made approximately equal contributions to a number of fields, use the number for the subject that provides the best common denominator, giving some extra consideration to the person’s occupation.” Giving extra consideration to Mesmer’s occupation as a physician, the comprehensive biography for him is 615.8512092 Hypnotherapy—Biography, where a work like Franz Anton Mesmer (1734-1815): kwakzalver of ontdekker van 'het onbewuste'? [quack or discoverer of the unconscious] should be classed.