This book challenges the conventional wisdom that improving democratic politics requires keeping emotion out of it. Marcus advances the provocative claim that the tradition in democratic theory of treating emotion and reason as hostile opposites is misguided and leads contemporary theorists to misdiagnose the current state of American democracy. Instead of viewing the presence of emotion in politics as a failure of rationality and therefore as a failure of full citizenship, Marcus argues that democratic theorists need to understand that emotions are in fact a prerequisite for the exercise of reason and thus essential for rational democratic deliberation and political judgement. Attempts to purge emotion from public life are not only destined to fail, but would ultimately rob democracies of a key source of revitalization and change. Drawing on recent research in neuroscience, Marcus shows how emotion functions generally and what role it plays in politics. In contrast to the traditional view of emotion as a form of agitation associated with belief, neurosciece reveals it to be generated by brain systems that operate largely outside of awareness. Two of these systems, "disposition" and "surveillance", are especially important in enabling emotions to produce habits, which often serve a positive function in democratic societies. But anxiety, also a preconcious emotion, is crucial to democratic politics as well because it can inhibit or disable habits and thus clear a space for the conscious use of reason and deliberation. Marcus concludes that if we acknowledge how emotion facilitates reason and is "cooperatively entangled" with it, then we should recognize sentimental citizens as the only citizens really capable of exercising political judgement and of putting their decisions into action.