In this paper, we argue for social psychology as 'a science of movement'. We argue that such a science must problematise the status quo and focus on the way in which social stability as well as social change is actively produced. Key to this project is a recognition that human action arises in a context where multiple voices seek to mobilise people in different directions. The question of which voice prevails depends upon processes of social identification that provide a basis for authority and influence. We illustrate this approach, first, by examining the dynamics of crowd behaviour. We use the Elaborated Social Identity Model (ESIM) to examine when people pay heed to those who advocate a challenge to authority and when, by contrast, participation increases their acceptance of existing authority. We then go on examine Milgram's famous 'obedience' studies, looking again at when participants shun the voice of authority and when they heed it. In contrast to conventional explanations which take conformity to authority as a given, we propose an 'engaged follower' perspective in which conformity depends upon identification with the cause which authority represents. We finish by showing how Milgram actively managed participants' identification in order to mobilise their compliance.