Hugh Everett, an American physicist, proposed the Relative State Formulation in which every possible outcome of every possible event exists in its own "history" or "world". He postulated the existence of an enormous number of universes and theorized that every possible event that never occurred in our particular past occurred in the past of these parallel universes. Everett's formulation was renamed the "many-worlds interpretation" (MWI) by the theoretical physicist Bryce DeWitt in the 1960s. Many-worlds regards reality as a many-branched tree, similar to the garden of forking paths, where every possible quantum outcome occurs