Foucault’s Pendulum (original title: Il pendolo di Foucault) is a novel by Italian writer and philosopher Umberto Eco. It was first published in 1988, and an English translation by William Weaver appeared a year later. Foucault’s Pendulum is divided into ten segments represented by the ten Sefiroth. The novel is full of esoteric references to Kabbalah, alchemy and conspiracy theory — so many that critic and novelist Anthony Burgess suggested that it needed an index. The pendulum of the title refers to an actual pendulum designed by the French physicist Léon Foucault to demonstrate the rotation of the earth, and has symbolic significance within the novel. Some believe it refers to the philosopher Michel Foucault, noting Eco’s friendship with the French philosopher, but the author “specifically rejects any intentional reference to Michel Foucault” — this is regarded as one of his subtle literary jokes.