Gabriele Contessa

In this paper, I argue that, contrary to the constructive empiricist’s position, observability is not an adequate criterion as a guide to ontological commitment in science. My argument has two parts. First, I argue that the constructive empiricist’s choice of observability as a criterion for ontological commitment is based on the assumption that belief in the existence of unobservable entities is unreasonable because belief in the existence of an entity can only be vindicated by its observation. Second, I argue that the kind of ontological commitment that is under consideration when accepting a scientific theory is commitment to what I call theoretical kinds and that observation can vindicate commitment to kinds only in exceptional cases.

Fictionalism and deflationism are two moderate meta-ontological positions that try to occupy a middle ground between the extremes of heavy-duty realism and hard-line eliminativism. Deflationists believe that the existence of certain entities (e.g.: numbers) can be established by means of ‘easy’ arguments—arguments that, supposedly, rely solely on uncontroversial premises and trivial inferences. Fictionalists, however, find easy arguments unconvincing. Amie Thomasson has recently argued that, in their criticism of easy arguments, fictionalists beg the question against deflationism and that the fictionalist alternative interpretation of easy arguments is untenable. In this paper, I argue that both charges are unsubstantiated. Properly understood, the fictionalist’s objection to ‘easy’ arguments takes the form of a dilemma—either the premises of ‘easy’ arguments are not truly uncontroversial or the inferences on which they rely are not truly trivial. Moreover, I argue not only that, contrary to what Thomasson claims, the fictionalist’s interpretation of easy argument is tenable but that the fictionalist might, in fact, have a better explanation of the seemingly trivial nature of the inferences involved in easy arguments than the deflationist’s.