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A referential theory of meaning for singular terms does
two things. First, it equates the meaning of a singular term with
its reference. In this way, such a theory links naming and meaning.
Second, it equates the reference of a singular term with a particular,
concrete or abstract. In this way, a referential theory avoids making
singular terms the vehicles of a strictly conceptual content.5
A referential theory thus assigns meanings in such a way as to satisfy
EX1.
EX1: The meaning
of a singular term is a particular.
An extensional semantics embraces a referential theory of meaning for singular
terms. Call a semantics which satisfies EX1,
EX1-extensional.
The second criterion for an extensional semantics is of a different
sort. Whereas EX1 equates the meaning
of a singular term with its reference, EX2
exacts a tribute from sentence meanings.
EX2: When in a
sentence, a singular term is substituted for another with the same meaning,
the meaning of the sentence remains constant.
It is sometimes supposed that a semantics which is EX1-extensional
must also be EX2-extensional:
If [singular terms] have no other semantic role
but to refer, then it appears that if two [singular terms] refer to the
same individual, then a principle...is warranted...that says that substitution
of one [term] for the other will...preserve...the proposition expressed.
(Donnellan [1990], p. 202)6
But this is not so. Whether a singular term's reference is its meaning,
and whether the meaning of a sentence remains constant when one singular
term is replaced by another with the same meaning, are separate questions--as
are whether "Hesperus" and "Phosphorus" mean Hesperus and Phosphorus, and
whether the meaning of "Hesperus = Hesperus" is the same as
that of "Hesperus = Phosphorus". Whether a theory of
meaning is EX1-extensional is independent
of whether it is EX2-extensional.
In my semantics, Hesperus and Phosphorus exhaust the meaning of "Hesperus"
and "Phosphorus". The EX2-semanticist
and I thus both commence by treating the referents of singular terms as
their meanings. But here we part ways. For the tribute exacted
by the EX2-semanticist's commitment to
Hesperus and Phosphorus is one that "Hesperus = Phosphorus" and "Hesperus
= Hesperus" cannot pay. And so the EX2-semanticist
casts out Hesperus and Phosphorus from the Garden of Meaning. I will
not recount the ensuing fall from semantic grace of extensions generally. |
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