The social psychology of crowds and masses has traditionally counterposed reason and emotion: specifically, the loss of identity and of reason in the crowd is held to lead to an excess of emotion. Crowds are represented as passionate, fickle and ever liable to excess. More recently, there has been a shift to emphasise the reasoned and meaningful nature of crowd action. It is constrained, normative and reflects the belief systems of the social groups that are involved. However, the emphasis on reason has been accompanied by a neglect of emotion. Crowds are treated as dispassionate phenomena. In this presentation, I will seek to integrate the reason and emotion of crowds using evidence from a range of crowd events, from riots in the UK to mass pilgrimages in India. First, I will examine the psychological transformations that occur when people become members of a unified crowd. Second, I shall show how shared social identity creates intimacy between people and thereby empowers people to act agentically, able to shape their own world rather than living in a world shaped by others. Third, I will show how intimacy and agency are experienced as extreme positives, accounting for the passion of crowds. In short, the emotion of crowds is tied to the enactment of reason, not its suppression.