Willard Van Orman Quine

Quine on Modality 211
5. Several of Quine’s insights concerning quantified modalities
continue to hold after one has given up one-sorted semantics:
the substitutivity of identity, the necessity of identity, and
Aristotelian essentialism.
Two-sorted semantics makes it possible to have contexts
that are referentially transparent, so that quantification into
them makes sense, and extensionally opaque, so that modal
distinctions do not collapse. This is just what Aristotelian
essentialism amounts to: We distinguish between necessary
and contingent attributes (extensional opacity), and the objects
over which we quantify have these attributes regardless
of the way in which the objects are referred to (referential
transparency).
Quine immediately rewrote the parts of From a Logical Point of
View that deal with modalities. In the new edition, which was out
that same fall, Quine carried out the following revisions. First, he
gave up the view that restricting the universe to intensional entities
will alleviate the situtation:
Actually, even granting these dubious entities we can quickly see that the
expedient of limiting the values of variables to them is after all a mistaken
one. It does not relieve the original difficulty over quantifying into modal
contexts; on the contrary, examples quite as disturbing as the old ones can
be adduced within the realm of intensional objects....
It was in my 1943 paper [NEN] that I first objected to quantifying into
modal contexts, and it was in his review of it that Church proposed the
remedy of limiting the variables thus quantified to intensional values. This
remedy, which I have just now represented as mistaken, seemed all right
at the time. Carnap [in Meaning and Necessity] adopted it in an extreme
form, limiting the range of his variables to intensional objects throughout
his system. He did not indeed describe his procedure thus; he complicated
the picture by propounding a curious double interpretation of variables. But
I have argued that this complicating device has no essential bearing and is
better put aside.
By the time Church came to propound an intensional logic of his own [in
“A Formulation of the Logic of Sense and Denotation”] he perhaps appreciated
that quantification into modal contexts could not after all be legitimized
simply by limiting the thus quantified variables to intensional values.
Anyway his departures are more radical. Instead of a necessity operator
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