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.
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)
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)
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.
“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.
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