Truth Condition and Entailment
The meaning of a sentence in terms of truth conditions on that
sentence is said to be equivalent to characterizing the meaning of a sentence
in terms of its logical form. Knowing the meaning of a sentence involves
knowing its truth-condition. A native speaker has intuitions about the
truth-condition of any given sentence in her language.
e.g.: Bill is a bachelor.
From that example we
may get some inferences, which are the necessary conditions for the truth of
the sentence, which can be derived, such as:
·
Bill has never
been married
·
Bill is a man
·
Bill is an adult
·
Bill is human
As we have known
together that the meaning of the sentence was characterized as the set of
conditions necessary and sufficient for the truth of the sentence. So that, in
case of our example, we may see that, Bill is a bachelor means Bill has never
been married. Why is it so? Because has never been married is a necessary
condition of being bachelor. Therefore, it must be true, when Bill is a
bachelor, Bill has never been married. And so on for every sentence, in which
any necessary condition will be an inference of that sentence simultaneously.
Another term which has
been used in place of inference is entailment. From the explanation
above, we may see that to give meaning of a sentence in terms of the necessary
and sufficient condition for the truth of that sentence is to provide a
specification from which entailments of a sentence can be derived by an
automatic procedure.
Since
the semantic relations of entailment, synonymy and contradiction are all
interdependent, the successful characterization of one of these terms will
guarantee that the other relations can be accounted for. Synonymy for example,
when two sentences have identical truth conditions, they must have the same
meaning. And when a sentence contradicts with another sentence, they must be
the negation for each other.
e.g.: Jane was certified as a doctor
Jane was declared as a doctor
From
that example, we may see that certified and declared are synonymy. Those words
have the same sense and identical truth. Therefore, when Jane was certified as
a doctor, it must be true that she was declared as a doctor.
e.g.: Bill is so staving
From
the sentence “Bill is so starving” stands in a relation of contradiction to
“Bill have eaten much” and “Bill is full”, in which the sentence “Bill have
eaten much” and “Bill is full” are the negations of “Bill is so starving”. If
Bill is full, of course Bill is not starving.
More
examples:
Entailment
whenever A is true, B
is also true.
(6) John is a
middle-aged American man.
a. John is male.
(6) entails (a)
(a) does not entail (6)
b. John is an American.
(6) entails (b)
(b) does not entail (6)
c. John is married.
(6) does not entail (c)
(c) does not entail (6)
Contradiction
whenever A is true, B
is false.
(7) John is a
middle-aged American man.
a. John is female.
(7) contradicts (a)
(a) contradicts (7)
b. John is a child.
(7) contradicts (b)
(b) contradicts (7)
c. John is married.
(7) does not contradict
(c)
(c) does not contradict
(7)
Remarks
When A entails B and B
entails A (i.e. A and B entail each
other), A and B have
the same truth-condition.
1. A entails B
? In all circumstances
where A is true, B is also true.
2. B entails A
? In all circumstances
where B is true, A is also true.
3. 1. and 2.
? A and B are true
under the same circumstances.
? A and B have the same
truth-condition.
When A contradicts B,
it necessarily follows that B
contradicts A. (i.e.
it’s impossible that A contradicts B but B
doesn’t contradict A).
Sentence meaning and
the non- declaratives
In this part we have seen how the interdependence between
meaning and truth can provide the basis for a theory of meaning, provided that
the concept of truth invoked is that of analytic truth rather than simply of
truth itself. The declarative sentence or declaration is the most important type.
A declarative sentence simply states a fact or argument, states an idea,
without requiring either an answer or action from the reader. It does not give
a command or request, nor does it ask a question. Declarative sentences consist
of a subject and a predicate. The subject may be a simple subject or a compound
subject.
For
example:
“His
name is John.”
In this sentence,
the subject is "his name" and the predicate is "is John".
Many people have pointed out that only
declarative sentences can be used to make statements, and so only these can be
true or false. There are many sentences in a declarative form which are no more
descriptions of events than are questions or commands.
Think for example:
- I promise that I will be there.
- I hereby agree that I was wrong.
- I suggest that he is innocent.
Sentences such as these
were first noticed by the philosopher J. L. Austin, who drew attention to the
untrue of assuming even that declarative sentences were consistently
description of event, which would be said to be true or false depending on the
correspondence or lack of it between the sentence and the non linguistic event
which the sentences described. Sentences of second type were said by Austin to
be used for performative utterance, so- called because they are not describing
anything but on the contrary constitute action. For example the very utterance
of a sentence such as (1) it is composed the performance of the action of
promising, the utterance of (2) itself an action of agreement, and utterance of
(3) the action of suggesting. This is
dramatic contrast to most declarative sentences: the utterance of I enter
the stage from the back does not itself constitute the act of entering, nor
is the utterance I can hear you now itself the action of hearing. Now
these performative utterances are important for linguists. So it shows that
speech act semantics can explain not only the properties of declaratives
sentences, as can a truth- conditional semantics, but also many of the areas
which prove problematic for truth conditional semantics.
REFRENCES:
Kempson,
M. Ruth. Semantic Theory. Cambridge University Press.
Suda, Yasutada. March 18, 2009. 24.900 Introduction to
Linguistics; Truth-Condition, Entailment, contradiction and Presupposition.
Retrieved from pdf
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