In any political setting, a few people will defy political authority. The main challenge for theories of rebellion is to explain when and why others join en masse. Scholarship on social movements typically develops answers to this puzzle on the basis of either of two microfoundations. Explanations that conceptualize individuals as utility-maximizers contend that they protest as a means to other ends. Explanations that see individuals as driven by values and beliefs suggest that people protest for the inherent benefit of voicing dissent. Both perspectives generate compelling explanations. Yet how do purposeful individuals act when utilitarian calculations and cherished values recommend contrary courses of action? Why might an actor prioritize one or the other at different points in time? Taking on these questions, I argue for an approach to microfoundations that focuses on emotions. Emotions such as fear, sadness, and shame promote pessimistic assessments, risk aversion, and a low sense of control. Such dispiriting emotions encourage individuals to prioritize security and resign to political circumstances, even when they contradict values of dignity. By contrast, anger, joy, and pride promote optimistic assessments, risk acceptance, and feelings of personal efficacy. Such emboldening emotions encourage prioritization of dignity and increase willingness to engage in resistance, even when it jeopardizes security. When instrumentality and values offer different answers to the question of whether to resign or rebel, therefore, emotions can shift individuals toward one or the other. I ground this argument in findings from the neurosciences and illustrate it with evidence from the 2011 uprisings in Tunisia and Egypt and the absence of an uprising in Algeria.