 The problem of suitably eking out the use of these defective nouns can be solved once for all by systematically fixing upon some suitable already-recognized object, for each \(x\) and \(y\), with which to identify \(\langle x,y \rangle\). The problem is a neat one, for we have in (1) a single explicit standard by which to judge whether a version is suitable. (Quine 1960, 258)