Examines and rejects several arguments claiming that the fundamental purposes of binary belief requires deductive cogency. The strongest such argument claims that if deductive cogency were not rationally required, deductive arguments would have no rational force. Develops and defends an alternative explanation of the epistemic importance of deductive arguments, rooted in a probabilistic coherence constraint on graded belief. Ends with a discussion of whether binary belief has any epistemic importance; argues that although our binary way of talking and thinking about belief may be very useful, it may not, in the end, capture any important aspect of rationality. Moreover, further development of extended Preface-type cases shows that the sort of binary belief that was subject to deductive cogency could not have the connections to central aspects of our practical reasoning, our assertions, and our emotions that seem to give belief its point.
Keywords: assertion, binary belief, deductive closure, deductive cogency, deductive consistency, emotions, graded belief, practical reason, Preface Paradox, probabilistic coherence, rationality,