Willard Van Orman Quine

Quine on Modality 209
This argument from 1960 was meant by Quine to clinch his case
against the modalities. After nineteen years of steadily stronger arguments,
he finally had something that came close to a proof that
if one quantifies into modal contexts, then the modal distinctions
collapse, in which case the modalities would no longer have any
point.
changes in quine’s view on the modalities
In the spring of 1961, Quine came to acknowledge the following
points:
1. There is something wrong with the argument from Word and
Object that we just went through. It applies not just to necessity
and possibility but to all operators that aim at singling
out from the class of all true sentences a proper subclass. An
argument parallel to that of Quine shows that the intended
distinction will collapse: The subclass will coincide with the
full class. Hence, for example, since ‘knows that’ is such an
operator, everything that is true will be known. Many other
notions also will collapse, such as probability, obligation, belief,
and so on.
2. By formalizing the argument so as to make its various assumptions
explicit, one finds that the argument makes no
assumptions that were not universally accepted in 1960.
3. The assumption that can most plausibly be given up is the
unified, or one-sorted, semantics that one finds in Frege,
Carnap, and many others, that is, the view that singular
terms, general terms, and sentences all have the same kind
of semantics – they have a meaning that determines their
reference.
4. If one assumes a two-sorted semantics, where general terms
and sentences behave as in standard Fregean semantics while
singular terms keep their reference “in all possible worlds”
(if one likes to speak that way), one can avoid the collapse
and make sense of quantification into modal contexts.
Restricting the universe to concepts or other intensional
entities has no point. It is the singular terms and not the
objects that matter. If the singular terms satisfy the condition
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