Abstract

In this journal, Peter Lipton and I discussed Musgrave's objection that the constructive empiricist cannot consistently maintain his own distinction between the observable and the unobservable, and van Fraassen's initial reply. We considered several possible interpretations of van Fraassen, and expressed misgivings about each. Muller and van Fraassen have consequently clarified the official constructive empiricist response to Musgrave, although some issues still remain.According to Muller and van Fraassen, Musgrave's objection assumes that constructive empiricism is to be understood in line with a syntactic account of our scientific theories – whereby a theory consists of a set of sentences formulated in some suitable language – whereas constructive empiricism has always been wedded to an explicitly semantic account of our scientific theories, which understands a scientific theory in terms of a class of models. Once this oversight is amended, the objection is seen to be toothless. As Muller and van Fraassen write: " Indeed, the only proper response, and the one that turns the table on Musgrave and his followers, is to argue that his incoherence argument does not work in the context of the semantic view as here elaborated, while the bad consequence he draws is an inevitable corollary to the older view within which he presents it. "The force of Musgrave's objection therefore turns on nothing more than implicitly saddling the constructive empiricist with an independently problematic account of what a scientific theory is.This move should cause some surprise however, for Musgrave's objection – albeit usually presented in conjunction with an explicitly syntactic construal of our scientific theories – is in fact quite neutral between these competing accounts. As Musgrave originally put it, in order for the constructive empiricist to draw his distinction between observable and unobservable …