PARTIAL-STATE FORMALISM AND THE OBJECT SUBJECT SPLIT IN QUANTUM-MECHANICS

A suitable general statistical framework is established by taking quan tum mechanics as full, and other (state-distinguishing) statistical th eories as partial theories with respect to a given relevant subset of observables. The partial theory exists and is unique up to equivalence . The choice of the simplest or canonical one is determined. The recen tly introduced hybrid, i.e., half quantum mechanical and half classica l discrete, statistical states obtain thus their rightful place in a h ierarchy of relevant quantum statistical theories. On the other hand, these states are shown to represent a derivation of the quantum object -subject split with a well-defined subject that encompasses preparator or measuring instrument in a natural way.