James M. Robins, Tyler J. VanderWeele Departments of Epidemiology and Biostatistics, Harvard School of Public Health Richard D. Gill Mathematical Institute, Leiden University Keywords : Interactions, interference, local reality, quantum physics. We give a simple proof of Bell’s inequality in quantum mechanics which, in conjunction with experiments, demonstrates that the local hidden variables assumption is false. The proof sheds light on relationships between the notion of causal interaction and interference between particles. arXiv:1207.4913v1 [stat.AP] 20 Jul 2012 1 Abstract A proof of Bell’s inequality in quantum mechanics using causal interactions