To feel what others feel: two episodes from 18th century medicine

In the late 18th century two medical fashions--Mesmerism in France and the Perkins 'tractor' in the USA and England--appealed to the principle that a single universal force acts on all of us and is responsible for health and illness. This principle served both fashions well, as it made it all the easier for those who came within their force fields to experience the sort of sensations that other subscribers to the fashion also seemed to feel. The first research on what is now known as the placebo effect was in connection with these two movements. The propensity to feel what we suppose or imagine that others like us feel remains even now one of the channels of the placebo effect.