 Sensible identity questions are those that can be asked from within a structure. They are those questions that can be answered on the basis of structural aspects of the structure. Identity questions that go beyond a structure do not make sense. One can pose the question whether \(3 \in 4\), but not cogently: this question involves a category mistake. The question mixes two different structures: \(\in\) is a set-theoretical notion, whereas 3 and 4 are places in the structure of the natural numbers. This seems to constitute a satisfactory answer to Benacerraf’s challenge.