G. K. Chesterton famously said something to this effect: When people stop believing in God, they don’t believe in nothing—they believe in anything. A good example of this is Umberto Eco’s novel Foucault’s Pendulum, in which a group of friends program a computer to “write” a book about secret hidden knowledge. Titled The Plan, the book is the result of random links between things like Kabbalah, Rosicrucianism, the Knights Templar, and other crackpot ideas. While The Plan was intended as a prank, other people take it seriously, with tragic results. Well, Foucault’s Pendulum shows us how gullible unbelieving people are....