Albert Einstein to Max Born, 4 December 1926
Both Heisenberg's and Schrödinger's approaches suffer from problems of physical interpretation. Schrödinger’s wave mechanics cannot explain the particle characteristics of electrons as their waves diverge. In reaction to this, Born develops the statistical interpretation of quantum theory in which the waves only describe the probability of an electron being found at a particular location. Einstein does not like the idea at all that this implies that wave mechanics is also indeterministic.