Ian Hacking's Experimental Realism about Theoretical Entities

Theoretical entities mean those unobservable entities which are taken for granted to explain observable indescribable phenomena in a theory. One of the most important issues which are always controversial in studying these entities and emphasized in the present paper is their ontological aspect. Can we believe in all these entities and accept their existential reality unconditionally? Should we reject all theoretical entities as myths constructed by scientists’ minds and try to establish a new science with no theoretical entity? Given the very important role we assign to this kind of entities in scientific explanation of events, their unobservablity has led to a very high sensitivity and formation of various and sometimes contradictory views about these entities. Two opposing views are realism and antirealism with different spectral classifications in terms of the rate of their commitment to constructive elements of each view. If none of these two views- realism and antirealism- can answer the question of ontological state of theoretical entities completely in their most radical manifestation, then we need to search for some criteria to help us indifferentiating real entities from myths which are merely constructed by mind. The present paper seeks to study the concept and status of theoretical entities in science and tries to achieve a proper criterion to judge about their objective reality in the framework of Ian Hacking’s experimental realism. It tries to review fundamental beliefs of important views about theoretical entities and emphasize on Hacking’s position by clarifying their status in science.