During the five years I worked as an environmental-studies professor at a progressive private college, I undertook a small, semesterly rebellion: I had students read “Confessions of a Recovering Environmentalist,” a 2011 essay by the British writer and former green radical Paul Kingsnorth. In it, Kingsnorth chronicles his disenchantment with the activism that had once been his life’s work—the very kind of advocacy that had driven many of my students, that had driven me, into that classroom in