Human life is pervaded by problems. Reasoning is a common response to problems we care about. We do it more than we notice; it is natural, often automatic, and need not call attention to itself. Reasoning is often associated with intellectual problems, such as what constitutes a just state, or whether a system of axioms is free of contradiction. But we also reason in response to everyday problems about how to get on with ordinary business. Confronted with a request for help at a time when we have planned something else, we must decide whether to decline or to adjust our schedule; given a roadblock, we must choose among detours.