The End of Eternity

The End of Eternity is a 1955 science fiction novel by Isaac Asimov with mystery and thriller elements on the subjects of time travel and social engineering. Its ultimate premise is that of a causal loop, a type of temporal paradox in which events and their causes form a loop. In The End of Eternity, members of the time-changing organization Eternity, known as "Eternals", seek to ensure that the conditions that led to its founding occur as history says that they occurred. At the end of the novel the protagonist, Andrew Harlan, is placed in a situation in which he must decide whether to allow the "circle" to close and Eternity to be founded or to allow the opposite to happen and prevent Eternity from having ever existed. Many years later, Asimov tied this novel into his broader Foundation Series by hinting in Foundation's Edge that it is set in a universe where Eternity had existed but was destroyed by Eternals, leading to an all-human galaxy later. The novel was shortlisted to the Hugo Award for Best Novel.