The Relational Interpretation of Quantum Mechanics

The Relation Interpretation of Quantum Mechanics is a refinement of textbook "Copenhagen" quantum mechanics, which is receiving increasing attention. It does not assume an absolute split of the world into "quantum system" and "classical observer"; it rather assumes that any physical system can play either role. It avoids the "many worlds" of some Everettian interpretations, the un-observable entities of Bomhiam interpretations, as well as the un-observed dynamical collapse of physical-collapse theories. The prices to pay is to accept that all physical quantities are relational, in the sense in which velocity is relational in classical mechanics: it expresses a relation between a system another system. I shall illustrate this understanding of quantum theory in detail and compare it with different and similar ways of viewing quantum mechanics.