Mark and I recorded this interview about a month ago, before the outbreak of protests across the world in support of the Black Lives Matter movement. A lot has changed since then. Conversations are different, as are the topics under discussion. This interview does not reflect those changes, at least not directly. Even so, a number of the topics in our conversation and in Mark's research more generally are relevant. In my hometown of Seattle, I watched these protests turn violent as the city toppled into rioting and chaos. And while individual acts of vandalism and looting are deplorable, there is no doubt that riots have played a crucial role in societal change over the course of history. When a riot spurs on regime change, we call it a "revolution." As you'll hear in our conversation, the societal, economic, and psychological causes of revolutions has been an underlying motivation in many of Mark's great ideas. In particular are his threshold models of collective behavior, which compare the spread of rioting to -- of all things -- an epidemic. Still, these abstract concepts can seem very distant from the heart of the matter while it's unfolding around us.