Even an Enlightenment skeptic reasoned that rational self-interest refutes medical murder conspiracies.

Evidence

Firstly, there is no doctor whatsoever who does not treasure his own personal interest and reputation more than the ruin of others. For this reason, he will seek to cure his patients, upon which his reputation depends and therefore also his personal interest. The only exceptions will be one or two individual cases of [judeoconverso] doctors who hope not to be detected [as a result of their high patient death rates]. There can be no doubt that a doctor at whose hands so many patients died would lose his reputation. Secondly, even if some were to succeed in their malevolent intent, then within two or three months everyone would flee from such a mortiferous doctor, even if they only attributed his patient death rates to his ignorance or bad luck. — James Renton, Ben Gidley (eds.), Antisemitism and Islamophobia in Europe, 424

Categorization

• DEEPTHINKING: An 18th-century skeptic deploys a reputation-and-incentive argument (pure rational-choice reasoning) to debunk a conspiracy myth — yet still cannot fully abandon belief; a striking demonstration that rational argument rarely dissolves prejudice.
• XREF: His reputation-and-patient-list argument is basically Milgrom’s repeated-game logic (cheating doctors lose reputations and patients within months) — early reasoning that anticipates modern extralegal enforcement theory.