It is a season of rethinking. Old assumptions are being reexamined. Years of economic stagnation punctuated by crisis; rising nationalist sentiment; shocking political developments throughout the world’s richest countries: All of it has left intellectuals of various stripes disoriented and unsettled.

You can see it on the left, where socialism is getting a new hearing. Progressives are losing faith that the neoliberal policies of the Clinton era are enough to counter rising inequality, restore economic growth, or beat back a populist Right. They also have a new sense that the limits of the possible have shifted. If Donald Trump can be …