Malcolm Gladwell spoke with The New Yorker’s Dorothy Wickenden in 2015 about the social dynamics of school shootings. Studying the literature of sociology, Gladwell compares shootings to a riot, in which each person’s act of violence makes the next act slightly more likely. And David Remnick speaks with the Columbia professor Mark Lilla, whose book “The Once and Future Liberal” argues provocatively that identity politics and support for marginalized groups are costing the Democrats election after election. “We cannot do anything for these groups we care about if we do not hold power—it is just talk,” Lilla says. “An election is not about self-expression—it’s a contest.”