This paper aims to demonstrate the fecundity of pairing specific insights from On Certainty with research in the philosophy and history of the natural sciences. To do so, it discusses one set of related themes in the work that focus on the possibility of and nature of revolutionary change. Specifically, I argue that several of Wittgenstein’s rather gnomic remarks presage van Fraassen’s insistence on the need for decisions and emotions throughout scientific revolutions. Moreover, I argue that reading both together enriches each’s individual account and helps further make sense of why and how conversion is not just a ‘mad leap in the dark’.