For months, Peter Thiel, the right-wing tech billionaire, has warned of what he sees as an imminent threat from the Antichrist, an entity portrayed in some Christian traditions as one of Jesus’ ultimate enemies. Mr. Thiel, an investor in artificial intelligence, says he is drawing on biblical prophesies to warn of an Antichrist who will promise safety from existential risks like nuclear war, climate change and artificial intelligence only to bring about something worse: one-world, totalitarian government. Now, Mr. Thiel is encountering resistance from Christian thinkers in the Roman Catholic Church, just as he tries to build support for his...