Abstract

Eight derivations of Bell’s inequality are given. First a simple and concrete derivation is given drawing on the full strength of the two hypotheses of locality and hidden variables. Two attempts at deriving Bell’s inequality without locality are made. They fail, but give valuable insight into the form which nonlocality must take in quantum physics. Arguments are given against this form of nonlocality. Ontological ideas which allow separation, realism, and locality in quantum mechanics are indicated. In the following five derivations, a number of variants of the assumption of hidden variables are tried. Among the insights which these derivations give rise to are: Particles cannot be assumed to have spin or polarisation values for as much as one fixed direction. The classical picture of electromagnetic radiation is incompatible with QM. Heisenberg’s idea of potentiality in elementary particles is incompatible with QM. There is a weakest form of hidden variables, called realisability, which is sufficient to yield Bell’s inequality. Quantum states cannot be identified with physical states. The mathematical problem of the integration of quantum states into physical states is nontrivial.