Rehder, W.2019-01-042019-01-0419800932-0784https://depositonce.tu-berlin.de/handle/11303/8806http://dx.doi.org/10.14279/depositonce-7935Necessary and sufficient conditions for commutativity of two projections in Hilbert space are given through properties of so-called conditional connectives which are derived from the conditional probability operator PQP. This approach unifies most of the known proofs, provides a few new criteria, and permits certain suggestive interpretations for compound properties of quantum-mechanical systems.en500 Naturwissenschaften und MathematikcommutativityprojectionsHilbert spaceArticle1865-7109