Empirical Adequacy and Ramsification

Structural realism has been proposed as an epistemological position interpolating between realism and sceptical anti-realism about scientific theories. The structural realist who accepts a scientific theory Θ thinks that Θ is empirically correct, and furthermore is a realist about the ‘structural content’ of Θ. But what exactly is ‘structural content’? One proposal is that the ‘structural content’ of a scientific theory may be associated with its Ramsey sentence R(Θ). However, Demopoulos and Friedman argued, using ideas drawn from Newman’s earlier criticism of Russell’s structuralism, that this move fails to achieve an interesting intermediate position between realism and anti-realism. Rather, R(Θ) adds little content beyond the instrumentalistically acceptable claim that the theory Θ is empirically adequate. Here, we formulate carefully the crucial claim of Demopoulos and Friedman, and show that the Ramsey sentence R(Θ) is true just in case Θ possesses a full model which is empirically correct and satisfies a certain cardinality condition on its theoretical domain. This suggests that structural realism is not a position significantly different from the anti-realism it attempts to distinguish itself from.