ABSTRACT
The preceding epigraph sounds like it could have been taken from a page of Hans Vaihinger’s (1911/1952) book on fi ctionalism, The Philosophy of ‘As If.’1 Instead, however, it comes from a recent article in a physics journal, coauthored by an experimental physicist at MIT (Dan Kleppner) and a theoretical physicist at the College of William and Mary (John Delos). Like Vaihinger, these physicists are defending the view that some fi ctions have a legitimate role to play in science, and also like Vaihinger they are defending these fi ctions on pragmatic grounds. Kleppner and Delos are concerned specifi cally with an area of research known as semiclassical mechanics, and the remarkable fertility of using fi ctional classical electron orbits to describe the quantum spectra of atoms placed in strong external fi elds. A striking feature of this research is that these fi ctional orbits are not simply functioning as calculational devices, but also seem to be playing a central role in the received scientifi c explanation of these phenomena. Although there is a growing recognition that fi ctions have some legitimate role to play in scientifi c theorizing, one function that is traditionally denied to fi ctions is that they can explain. Even Vaihinger, who argues for the pervasiveness of fi ctions in science, rejects the view that there are explanatory fi ctions.
