In this book, I will argue that contentious politics emerges in response to changes in political opportunities and threats when participants perceive and respond to a variety of incentives: material and ideological, partisan and group-based, long-standing and episodic. Building on these opportunities, and using known repertoires of action, people with limited resources can act together contentiously – if only sporadically. When their actions are based on dense social networks and effective connective structures and draw on legitimate, action-oriented cultural frames, they can sustain these actions even in contact with powerful opponents. In such cases – and only in such cases – we are in the presence of a social movement. When such contention spreads across an entire society – as it sometimes does – we see a cycle of contention. When such a cycle is organized around opposed or multiple sovereignties, the outcome is a revolution.

The solutions to the problem of mobilizing people into campaigns and coalitions of collective action depend on shared understandings, social networks, and connective structures and the use of culturally resonant forms of action. But above all – I shall argue – they are triggered by the ebb and flow of political struggle. In this chapter, I will lay out each of these factors as they will be used in this book to describe, analyze, and raise questions about contentious politics and social movements.