On a Derivation of the Necessity of Identity - Princeton University

Given the general character of Quine’s complaint, as paraphrased by
Church, there is reason to speculate that already in 1946 Quine may have had in
mind the replacement of the “laborious” (11)-(15) by the “obvious” (1)-(3). But if
one so speculates, one will need to explain the curious fact that when Quine came
to write a review [1947b] of the third Barcan paper for the JSL, he made not one
mention of the result on the necessity of identity. I think this can be explained, but
the story is neither short nor simple.
The first thing that needs mentioning is that Quine’s review also made not
one mention of the other main result of the third Barcan paper, the coextensiveness
of “material” identity as defined by Russell with “strict” identity as defined by
Marcus. Quite the contrary, after noting that there are two identity definitions (7)
and (8) in play from early in the paper, Quine launches into a sermonette against
the idea of “degrees of identity”, as if Marcus were advocating such a notion, and
as if her two definitions were intended as characterizations of two different
“degrees”. Quine here is overlooking the fact that Marcus’s explicit goal is
precisely to prove the two definitions coextensive.
Quine’s oversight is pointed out in the Fitch footnote cited earlier. Fifteen or
so years later the review apparently still rankled, since in her much-discussed
February, 1962 talk at the Boston Colloquium for the Philosophy of Science,
Marcus goes out of her way to work in a semi-jocose allusion to that old episode. 7
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