PHL313: Some Observations about Truth Theories
Some Observations about Truth Theories
Basic Truth Theories of Meaning
The basic intuition is straight-forward: those who advocate the
truth-based theories of meaning argue that a theory of what it is for
an utterance to be true in a language would also provide a theory of
meaning for that language.
Recall the T-Biconditionals. The idea is that we would have a theory
of truth for a language if we had a theory that could, for every
sentence S in our language, produce a sentence of our theory that had
"S" is true in L (at time t and place xyz) if and only if p
Where p is some kind of recursive analysis in our theory and reveals
precisely the conditions under which S is true or not. Parts of
language which are not themselves true or false will have their
meaning then explained in terms of how they can contribute to the
truth or falsity of various declarative sentences. That is, the
difference in meaning between "Seagulls" and "Cats" will in part be
explained by the different roles that these natural kind terms play in
sentences like "Seagulls are birds" or "Cats are birds" and so on.
We discussed six problems with this basic version of the truth-based
theory of meaning.
We discussed Davidsonian replies to the first four. But a widely
accepted way of handling the latter two is to add modal notions to
our theories of meaning.
- Contradictions and paradoxes
- Vagueness and ambiguity
- nondeclarative sentences
- possibility and other modal notions
- co-extensive terms or truth-conditions
A revised tuth-based theory: the possible-worlds theory of meaning
One way that has been proposed to improve the truth-based theory is
the hypothesis that meaning is not given in just truth conditions.
Rather, it is given in all possible truth conditions.
On the truth-based theory, utterances S1 and S2 have the same meaning
if they have the same truth conditions (in this world). This is why
co-extensive terms or predicates are a problem.
On the modal-extension of the theory, utterances S1 and S2 have the
same meaning if they necessarily have the same truth conditions.
Define a possible world to be a complete consistent description of how things
could be. Define necessarily true as meaning true in all possible. Define
possibly true as meaning true in at least one possible world.
Thus, on this view, "bachelor" and "unmarried male" are true of all
and only the same things in every possible world. So, they have the same
"Has a kidney" and "Has a liver" are true of different things in some possible
worlds, and so they do not have the same meaning.
Note: When we say this, we always mean to fix the use of the
utterance we are describing in this the actual world. There is some
possible world where the sound of the word "bachelor" means rocks or
some other weird thing. But when we talk about what is necessarily or
possibly true of bachelors, we use the word "bachelor" only as it is
used in this world in our language, and then look at the things that
we may be concerned with in various different possible worlds. This
is very important. We are using our language in this world to refer
to those other worlds.
This extension of the theory handles both the problem of how do we
make sense of sentences like, "Lincoln could have avoided
assassination" -- this means that there is a possible world in which
he was not assassinated. And it makes sense of how coextensive terms
can have different meaning: they may be only accidentally (and not
A large and ongoing program in linguistics has been to develop and
analyze natural languages using what is called "Montague Grammar" or
"Montague semantics." This is a formal system for describing a
natural language, and named after the logician Richard Montague. The
system uses modal notions along with classical logical tools. This
formal system is meant to be a modal-logic that will provide a
truth-based theory of meaning for a natural language.