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Syntax / Theory / Fraassen: the syntactic approach distinguishes between observation terms and theoretical terms (TT). - Later, between "old" and "new" vocabulary. FraassenVs: The empirical importance (of observational consequences) can not be isolated - if they would be isolated, the extended theory would say the same thing about what is observable and how the observed behaves and nothing else.
B. van Fraassen
The Scientific Image Oxford 1980