What is identity politics? Is it, to paraphrase Dylan Thomas, a part of society you don’t like that’s fighting for its interests as fiercely as yours does? Or is it, as Mark Lilla puts it in The Once and Future Liberal, ‘a pseudo-politics of self-regard and increasingly narrow and exclusionary self-definition’? The book belongs to the genre of responses to Donald Trump’s election in which liberal American academics turn their rage on their own intellectual-political class. Lilla argues that the pursuit of identity politics by liberal graduates has crippled and distracted the Democrats.