 From the birth of the theory of quantum mechanics in 1925/6 to the outbreak of war in Europe, a clear orthodoxy emerged in the conceptual and ontological framework for understanding quantum theory. Now known as the Copenhagen interpretation, this framework embodied the positivistic tendencies of Heisenberg and Bohr, and was set opposed to the more realist tendencies of de Broglie, Einstein, and Schrödinger. It was not until Bell’s theorem in the 1960s, and its experimental tests in the 1970s and 1980s, that new energy was breathed into this interpretational debate. However, beginning in the mid-1940s, the first suggestions of retrocausality as part of the conceptual and ontological framework in quantum theory had already materialized.