I was thinking more about Gabriele's post on the semantic view of theories. Consider this quick argument in favour of a semantic view of theories:
- Scientists believe (or at least accept) scientific theories;
- Attitudes like belief and acceptance are held to propositions (certainly belief and acceptance ascriptions involve embedded 'that' clauses which seem to denote propositions);
- So, scientific theories are propositions.
This is pretty clearly a semantic view of theories. But Gabriele, and I presume others, seem not to believe this is the semantic view of theories, as discussed in the literature. Could someone explain the difference, if there is one? For I do not at this stage see it, for reasons I'll now explain.
The conclusion of this argument is what I have always understood to be the semantic view of theories. If propositions are structured (i.e., not just sets of possible worlds), then the propositions which express scientific theories can easily be models in the model-theoretic sense; if theories have merely qualitative content, no one model will capture the proposition expressed (as qualitatively indistinguishable models will equally satisfy the theory), so the proposition expressed should be a set of models. (Things seem to be a little, but not much, trickier if propositions are unstructured.) In any case, there seems to be a clear correspondence between the propositions expressed by the sentences of some presentation of the theory and the models which satisfy those sentences, a close enough correspondence that reducing the one to the other doesn't seem unreasonable.