This chapter outlines Bayle’s mature vision of the best worldview that could be produced by a perfectly rational human mind, as advanced especially in some of the most famous articles in the Dictionnaire and in the Continuation des Pensées Diverses. It is shown that Bayle owed a huge debt to the Gassendi and his successors on this score, taking the most rational philosophy available to a pagan to be an atheistic monism in which the first principle was immanent in the world. Bayle’s sources were exactly those identified in I.3 as following Gassendi on this matter (Thomasius, Bernier, Parker), as well as the anti-Jesuit accounts of Chinese and Japanese religion. But for Bayle the philolosophico-theological payoff of this genealogical vision was not recourse to Gassendi’s own philosophy, but rather to Malebranche’s occasionalism, which for Bayle was the only possible ‘Christian philosophy’. This elaborate historicisation therefore allowed Bayle to make a natural-theological argument, which was deployed against Spinoza among others. But at the same time, Bayle also acknowledged the explanatory limits of Cartesian occasionalism, above all when it came to issues stemming from the incomprehensibility of mind-body interaction: the ‘place’ of immaterial substances and animal rationality. This position was neither scepticism nor fideism, but an argument about the practical limits of philosophy.