Observable and theoretical entities in psychological measurements

It is outlined some issues of psychological measurements referred to observable and unobservable (theoretical) entities. From scientific realism and scientific instrumentalism perspectives it put forward the extent to which a scientific concept (that leads to measurements) and an empirical generalization (based on measurements) may be considered as theoretical (unobservable) entities. Of particular importance with respect to the unobservable (theoretical) entities are their considerable states. The basic theoretical overdetermination argument is introduced. It focuses on excessive meanings of a scientific concept as compared to measurements that depart from the concept containing a meaning solely. Either an application of the basic empiricist underdetermination argument to measurements is proposed.