Early recorded examples of the idea of infinite worlds existed in the philosophy of Ancient Greek Atomism, which proposed that infinite parallel worlds arose from the collision of atoms. In the third century BCE, the philosopher Chrysippus suggested that the world eternally expired and regenerated, effectively suggesting the existence of multiple universes across time. The concept of multiple universes became more defined in the Middle Ages . In Dublin in 1952, Erwin schrodinger gave a lecture in which he jocularly warned his audience that what he was about to say might "seem lunatic". He said that when his equations seemed to describe several different histories, these were "not alternatives, but all really happen simultaneously". This sort of duality is called "superposition ". The American philosopher and psychologist William James used the term "multiverse" in 1895, but in a different context. The ...