In the long term, protests work because they can undermine the most important pillar of power: legitimacy. Commentators often note that a state can be defined by its monopoly on violence, a concept going back to the philosopher Thomas Hobbes and codified by the sociologist Max Weber. But the full Weber quote is less well known. Weber defined the state by its “monopoly of the legitimate use of physical force.” The word legitimate is as important as the words physical force, if not more. Especially in the modern world, that monopoly on violence isn’t something that self-perpetuates. Violence doesn’t just happen; it has to be enacted and enabled by people. The Soviet Union did not fall because it ran out of tanks to send to Eastern Europe when the people there rebelled in the late 1980s. It fell, in large part, because it ran out of legitimacy, and because Soviet rulers had lost the will and the desire to live in their own system. Compared with Western democracies, their system wasn’t delivering freedom or wealth, even to the winners. If the loss of legitimacy is widespread and deep enough, the generals and police who are supposed to be enacting the violence can and do turn against the rulers (or, at least, they stop defending the unpopular ruler). Force and repression can keep things under control for a while, but it also makes such rule more brittle.

Legitimacy, not repression, is the bedrock of resilient power. A society without legitimate governance will not function well; people can be coerced to comply, but it’s harder to coerce enthusiasm, competence, and creativity out of a discouraged, beaten-down people. Losing legitimacy is the most important threat to authorities, especially in democracies, because authorities can do only so much for so long to hold on to power under such conditions. Maybe they can stay in power longer in part through obstacles such as voter repression, gerrymandering, and increasing the power of unelected institutions, but the society they oversee will inevitably decline, and so will their grasp on power.

In that light, focusing on legitimacy as the most robust source of power, it becomes clear that the Black Lives Matter movement has been quite successful in its short life.