 Quine (1950) has suggested that when a predicate is an I-predicate in a theory only because the language in which the theory is expressed does not allow one to distinguish items between which it holds, one can reinterpret the sentences of the theory so that the I-predicate in the newly interpreted theory does express identity. Every sentence will have just the same truth-conditions under the new interpretation and the old, but the references of its subsentential parts will be different. Thus, Quine suggests, if one has a language in which one speaks of persons and in which persons of the same income are indistinguishable the predicates of the language may be reinterpreted so that the predicate which previously expressed having the same income comes now to express identity. The universe of discourse now consists of income groups, not people. The extensions of the monadic predicates are classes of income groups, and, in general, the extension of an n-place predicate is a class of n-member sequences of income groups (Quine 1963: 65–79). Any two-place predicate expressing an equivalence relation could be an I-predicate relative to some sufficiently impoverished theory, and Quine’s suggestion will be applicable to any such predicate if it is applicable at all.