 This subsection is largely about two pairs of papers: “Probabilities of Conditionals and Conditional Probabilities” (1976b) and its sequel (1986h), and “Desire as Belief” (1988b) and its sequel (1996a). The papers have more in common than merely having a common naming convention. (They’re not even Lewis’s only sequels; “Lucas Against Mechanism” (1969b) also has a sequel (1979d).) In both cases Lewis aims to defend orthodox  Bayesian epistemology  against some challenges. And in both cases the argument turns on principles to do with updating. Lewis was throughout his career a Bayesian; he frequently said that the ideal epistemic agent was a Bayesian conditionaliser and expected utility maximiser. And he defended this position with some gusto.