SEMANTICS
Page 62
4. 2The Relation Among Statements I The Basic StatementsThere are relations among
the types of statement such as,
synonymy, entailment, inconsistency, etc.
Like synonymy, can be expressed as bidirectional entailment : Xis synonymous with Y means as the same with X entails Y and entails Y and
Y entails X. this will agree with our previous example He is an orphan is synonymous with
X
-
He is a child and have no father and mother.
Y
-
He
is an orphan entailsX
-
He is a child and have no father and mother.
Y
(and vice versa)
But if we say X entails Y, it doesn’t mean that Xis synonymous with Y,
like He is an orphan entails.
X
-
He has no father.
Y
SEMANTICS
Page The inconsistency of X and Y can be expressed as entailment relation between X and the negation of Y, and between Y and the negation of X. We can see them in the following John
is alive is inconsistency withX
-
John is dead.
Y
-
John is alive has an entailment relation with
X-
John is dead.
Neg Y
It seems that inconsistency can also be expressed as Xis synonymous with the negation o Y, and Y is synonymous with the negation of X. It is seen in
the fact that the negation of John is dead is synonymous with
John is alive.We can also express tautology and contradiction
in term of entailment ; a contradiction is a proposition whose negation is tautology,
and a tautology is a proposition which is entailed by all other propositions.
Let’s prove this with examples Xis a contradiction :
Kings are women.X
The negation of contradiction is tautology.
(neg X = Tautology) :
Kings are women. SEMANTICS
Page A tautology is a proposition which is entailed by all other propositions (Xis entailed by all other proposition) :
Kings are men is the entailment of :
X
Kings are women.
Monarches are kings.
Kings bark.
Etc.
From our analysis of relation
among the types of statement, it is true what Leech expressed that all basic statements can be translated into statements about entailment.
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