A foundational principle for quantum mechanics

In contrast to the theories of relativity, quantum mechanics is not yet bas ed on a generally accepted conceptual foundation. It is proposed here that the missing principle may be identified through the observation that all kn owledge in physics has to be expressed in propositions and that therefore t he most elementary system represents the truth value of one proposition, i. e., it carries just one bit of information. Therefore an elementary system can only give a definite result in one specific measurement. The irreducibl e randomness in other measurements is then a necessary consequence. For com posite systems entanglement results if all possible information is exhauste d in specifying joint properties of the constituents.