The American left’s embrace of divisive identity politics has, in Lilla’s view, contributed to the rise of Donald Trump and to an outbreak of angry and dangerous identity politics on the right. Essentially, Lilla wants to reopen the debate that broke out in the late 1960s between the “Old Left,” which emphasized class and economics and was rooted in classical socialist politics, and the “New Left,” which focused more on race and identity. The gap between working-class white voters and the Democratic Party that contributed to Trump’s election is, Lilla argues, the natural and inevitable consequence of the triumph of the New Left, which retreated from the world of mass politics to the groves of academia. Lilla’s sweeping summaries of major events and complex arguments sometimes seem glib, and he never really comes to grips with the connection between the decline of the industrial working class and the rise of the New Left. But his concern that the sometimes illiberal forms of identity politics appearing on the left can both provoke and enable illiberal forces on the right deserves serious consideration.