wasn’t clear at first why Peter Thiel agreed to talk to me. He is, famously, no friend of the media. But Thiel—co-founder of PayPal and Palantir, avatar of techno-libertarianism, bogeyman of the left—consented to a series of long interviews at his home and office in Los Angeles. He was more open than I expected him to be, and he had a lot to say. But the impetus for these conversations? He wanted me to publish a promise he was going to make, so that he would not be tempted to go back on his word. And what was that thing...