1. Hacking's entity realism

「If you can spray them, then they are real」(Hacking, 1983: 22). This well-known sentence best summarizes Professor Hacking's entity realism. In other words, if electrons can be sprayed (manipulated), then one can plausibly judge that electrons are real. The reasons for this judgment will be strong enough when electrons have been manipulated because any manipulated object must exist. Therefore, you do not need a theory about electrons to warrant your judgment. This reasoning makes Hacking separate realism about entities from realism about theories; the latter inquires whether a theory is true and the former inquires whether an entity really exists. Entity realists indeed claim that we can have good reasons to believe that an unobservable entity posited by a scientific theory really exists without believing that the theory is true. As an entity realist, Hacking even commits to an anti-realist position about theories, and he is not a radical realist about entities either. Some extragalactic entities, such as the gravitational lens in contemporary astronomy, for Hacking, cannot be embodied as an ontological reality because 「[g]alactic experimentation is science fiction, extragalactic experimentation is a bad joke」 (Hacking, 1989: 559). Thus, Hacking's realism has a position and ground entirely based on experimentation, as well as an attitude radically different from realism about theories. Following Resnik, I call Hacking's entity realism experimental realism.