A naïve Bayes approach to theory confirmation is used to compute the posterior probabilities for a series of four models of DNA considered by James Watson and Francis Crick in the early 1950s using multiple forms of evidence considered relevant at the time. Conditional probabilities for the evidence given each model are estimated from historical sources and manually assigned using a scale of five probabilities ranging from strongly consistent to strongly inconsistent. Alternative or competing theories are defined for each model based on preceding models in the series. Prior probabilities are also set based on the posterior probabilities of these earlier models. A dramatic increase in posterior probability is seen for the final double helix model compared to earlier models in the series, which is interpreted as a form of “Bayesian surprise” leading to the sense that a “discovery” was made. Implications for theory choice in the history of science are discussed.

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Handling Editor: Ludo Waltman

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