It is a variation of realism (independently proposed by Stanford School philosophers Nancy Cartwright and Ian Hacking in 1983) that restricts warranted belief to only certain entities.
As Ian Hacking, the main proponent of this formulation of entity realism, puts it (referring to an experiment he observed in a Stanford laboratory, where electrons and positrons were sprayed, one after the other, onto a superconducting metal sphere), "if you can spray them, then they are real.
"[3] Entity realism has been an influential position partly because it coincided with a general trend in philosophy of science, and science studies more generally, to downplay the role of theories and put more emphasis on experimentation and scientific practice.
[5] While many philosophers acknowledge the intuitive pull of entity realism, it has also been strongly criticised, both as being too restrictive (in that it ignores entities that are observable yet do not lend themselves to manipulation)[6] and as being too permissive (to the extent that seemingly successful instances of manipulation may turn out to be spurious).
[1] Psillos also remarks that to a certain extent "this scepticism about theories is motivated by none other than the argument from the pessimistic induction".