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In the eighteen century, serious thought about the impact of medical intervention concentrated on one question: the merits of inoculation againts smallpox. The procedure was simple: a thread covered with pus from a fresh pock on someone mildly infected with smallpox was pressed into a cut on an arm and on a leg of someone who had not yet had the disease. This usually resulted in a very mild case of smallpox, from which the individual rapidly recovered, and remained henceforth immune against further attacks. Smallpox inoculation had been practised in Turkey, China, and Elsewhere, but was first publicized in Northern Europe by Lady Mary Wortley Montagu, who had lived in constantinople (and who herself was seriously disfigured by …ver más…

You could not reduce, d'Alembert argued, the sort of decision involved in deciding to be inoculated to a simple cost-benefit analysis. There was no simple ratio that would allow one to weigh an increased life expectancy against a risk of immediate death.
In the 1750s inoculation techniques in England were greatly improved, the infected matter now being introduced under the skin rather than into the bloodstream. The procedure was safer. The practice of first bleeding and purging people before inoculation,and of subjecting them to a special diet and a period of rest lasting for a month prior to the operation, in order toensure they were fighting fit, was abandoned. Inoculation thus became cheaper, and consequently more widespread.
But a person inoculated against smallpox was capable of giving the disease in its virulet form to anyone they contacted. Early calculations of the number of lives that might be saved by inoculation made no attempt to factor in the number of people who migth be infected as a result ofinoculation. While smallpox was endemic in large cities such as London, and almost everyone was explosed to it sooner or later, it was epidemic in smaller towns and villages. In Chester, for example,one person died of smallpox in 1773, but 202 died (more than one third of all deaths) in 1774. In small towns and villages some people may have escaped exposure throughout their lifetimes. To inoculate a few people in