Abstract: This chapter examines van Fraassen's conception of rationality. It reviews the Bayesian structural conception of rationality and argues that it has been found wanting. It goes on to analyze van Fraassen's voluntarism. Some objections are raised about van Fraassen's reliance on prior opinion, and it is argued that the content of a belief matters to its rationality. Then it criticizes van Fraassen's view that inference to the best explanation is incoherent. Finally, it is shown that van Fraassen's conception of rationality is too thin to capture rational judgement fully.

Keywords: Bas van Fraassen, voluntarist, rationality, inference, rational judgement,