Bas van Fraassen has formulated a semantical or model theoretic analysis of the structure of scientific theories. He contrasts his semantical approach with the syntactic approach of the logical positivists and argues that his theory is preferable on a number of grounds. My aims in this paper will be threefold. First, I will present a brief description of van Fraassen's approach. Secondly, I will compare his theory with that of the logical positivists and, in so doing, identify the virtues that van Fraassen believes recommend, his theory over the positivist theory. Finally, I will raise an objection that is positivist in spirit which suggests that, epistemically, his account is indistinguishable from classical historicism.

For van Fraassen, “To present a theory is to specify a family of structures, its models; and secondly, to specify certain parts of these models (the empirical substructures) as candidates for the direct representation of observable phenomena.