 Although both defended two-tiered conceptions of inquiry, there are important differences between Kuhn and Carnap (as Friedman, 2001, 2003, 2010, among others, observes). For Carnap, as for Reichenbach, the choice of framework or coordinating definitions was conventional, a matter of convenience or heuristic fertility, whereas for committed Kuhnian normal scientists the foundational tenets of their paradigm are deep truths about the world, principles not subject to empirical test. (However, in a crisis situation, fertility becomes a key element in theory and paradigm choice.) In Carnap’s frameworks these were explicit systems of logical rules, whereas Kuhn’s account of normal science largely jettisoned rule-based knowledge in favor of a kind of case-based tacit knowledge, the cases being the concrete exemplars. Third, Kuhn himself emphasized that his approach was historical, whereas Carnap’s was not. Although a Carnapian change from one logical framework to another could, in principle, be quite revolutionary, Carnap himself never emphasized this point, suggested nothing of Kuhn’s radical discontinuity, and was simply not interested in the history of science.