 Reply: The distinction between identity and similarity statements (or sentences) is usually drawn in terms of the distinction between substantival and adjectival common nouns. If \(F\) is a common noun standing for a kind of things e.g., ‘horse’, then ‘\(x\) and \(y\) are the same \(F\)’ is a statement of identity, whereas if \(F\) is an a common noun standing for a kind of properties of things, then ‘\(x\) and \(y\) are the same \(F\)’ is a statement of similarity. (It’s interesting to note that when the noun is proper, i.e., a proper name, the result is a statement of similarity, not identity — as in ‘He’s not the same Bill we knew before’.) This distinction rests ultimately on the metaphysical distinction between substance and attribute, object and property. While the distinction no doubt presupposes the concept of individuation (the bundle theory, for example, presupposes that we have the means to individuate properties), there is no obvious reason to suppose that it entails the denial of RI, i.e., the claim that no instance of RI is true. For a beginner’s review — from an historical perspective — of the issues concerning substance and attribute, see O’Connor, (1967); and for more recent and advanced discussion and bibliography, see the entry on  properties.