 The Ramsey-sentence \(^{R}T\) that replaces theory T has exactly the same observational consequences as T; it can play the same role as T in reasoning; it is truth-evaluable if there are entities that satisfy it; but since it dispenses altogether with theoretical vocabulary and refers to whatever entities satisfy it only by means of quantifiers, it was taken to remove the issue of the reference of theoretical terms/predicates. ‘Structural realism’ was suggested to be the view that: i) scientific theories issue in existential commitments to unobservable entities and ii) all non-observational knowledge of unobservables is structural knowledge, i.e., knowledge not of their first-order (or intrinsic) properties, but rather of their higher-order (or structural) properties. The key idea here was that a Ramsey-sentence satisfies both conditions (i) and (ii). So we might say that, if true, the Ramsey-sentence \(^{R}T\) gives us knowledge of the structure of the world: there is a certain structure which satisfies the Ramsey-sentence and the structure of the world (or of the relevant worldly domain) is isomorphic to this structure.