SENTENCE RELATIONS
Objectives
Identify and explain specific sentence relations: synonymous, entailment, contradiction, presupposition and tautology.

Identify presupposition using presupposition triggers: definite expressions, cleft sentences, lexical triggers, change of state verbs.
Describe presupposition from both the semantic and pragmatic perspective and explain presupposition failure.

Introduction
Just like words exhibit relations with one another in a languge, sentences also relate in specific ways.
Such relations may be by reason of the use of particular words or by reason of certain syntactic structure.
Before discussing specific relations, it is important to briefly examine certain concepts which are crucial for the understanding of sentence meaning.
Truth, truth value and truth conditions
study of logic has contributed to the appreciation of meaning in sentences particularly the development of the criteria for processing meaning within sentences.
Sentence meaning has therefore been closely associated with truth value and truth conditions.
Alfred Tarski asserts that to know the meaning of a sentence is to know its truth conditions.
So what is truth?
The truth of a sentence consists in its agreement with or correspondence to reality.

When a sentence is true, semanticists say that it has truth value.

A true sentence therefore correctly describes the state of affairs in the world.
Thus the extension of a sentence is its truth value which may be true or false depending on whether or not the sentence depicts the actual world. The conditions or circumstances that will have to obtain in reality to make a sentence true or false are its truth conditions.
Consider the following examples:
Botswana obtained independence from Britain in 1966(T)
Botswana obtained independence from Britain in 1956(F)
Sentence 2 is false because the proposition expressed therein does not line up with historical evidence.
John believes that Botswana obtained its independence in 1956.

Sentence on the other hand is true as long as the following conditions hold: John exists and John holds this view. The two therefore constitute the truth conditions for sentence 3.
Note however that the sentence is true as long as these conditions are met even though a part of the sentence contradicts world view.
This is an indication that an entire sentence may have truth value T even if one or more parts therein are false.
Propositional content
Two sentences have the same propositional content if they both have the same truth conditions:
Tebogo took out the garbage
Tebogo took the garbage out.
A proposition is that part of the meaning of an utterance or sentence which describes some state of affairs.
The state of affairs typically involves persons, or things referred to by expressions in the sentence:
I have not read this book
This book, I have not read
It is this book that I have not read
Sentences 6, 7, and 8all have the same truth conditions and therefore express the same propositions though they have different thematic meaning, which is determined by the way speakers present what they are talking about in relation to particular contextual presupposition.
The sentence relations listed above can be explained using truth conditions.
Sentence relations
When dealing with meaning of sentences, we want to know:
What semantic relations hold between sentences of a language?
We look at an approach to meaning based on the notion of TRUTH.

Thus we will examine closely how successful a truth-based approach is in characterizing the semantic relations of entailment and presupposition.

To do this, we go back to the question ‘What is meaning?’ When a native speaker of a lang understands the meaning of a sentence, what do they know?
Thus, a semantic theory should reflect an English speaker’s knowledge. This knowledge includes:
Entailment relations: A entails b = If A, then au tomatically b.

Jane is Karabo’s wife. Entails:
Jane is married.

iii. Jane failed her Form Five examinations entails
iv. Jane took Form Five examinations.

Synonymous relations : A has the same meaning as b.

My sister is a divorcee.

My sister is no longer married.

Contradiction: A is inconsistent with b
Mary’s mother died last year.

Mary’s mother is alive.

Presupposition : A presupposes B if B is part of the assumed background against which A is said.

The Vice Chancellor of the University of Botswana is retiring.

The University of Botswana has a vice chancellor.

Tautology : A is a tautology if A is automatically true by virtue of its own meaning but informationally empty.

Poor people are poor.

Water is water.

When we study sentence meaning through logic, we are concerned about:
The truth of statements
Whether truth is preserved or lost by putting sentences into different patterns
Synonymous sentences
Two sentences p and q are synonymous if they both have the same truth value, that is if p describes a situation, q will also describe the same situation. Such sentences are referred to as paraphrases:

Jones owns the house
The house belongs to Jones
The composite truth table for the synonymous sentences above is as follows
Pq
TT
FF
T?T
F?F
The table is also applicable to 11 and 12 below. However the synonymous relation in this pair is induced by the syntax of the sentences.
The police pursued the robber
The robber was pursued by the police
Contradiction
Two sentences p and q are contradictory if they both affirm and deny the same proposition. For such sentences, when p is T q is F as shown below:
He is a bachelor
He is married
Pq
TF
FT
T?F
F?T
If he is constant in 13 and 14, then the two sentences are contradictory
Entailment
A sentence P entails sentence q if the truth of q follows necessarily from the truth of p:
The zookeeper killed the lion
The lion is dead
For 15 and 16 If p is true, then q is necessarily true. Similarly if q is false, then p is also false. However if p is false, then q may be true or false
Pq
TT
FT or F
F?F
T or F?T
Note that the entailment in 15 and 16 is a result of the lexical relationship between killed and dead.
Entailment may be mutual or asymmetrical.
If the lion is killed then it is dead. However the lion may be dead without being killed by someone.
Therefore the entailment in 15 and 16 is asymmetrical.
On the other hand, sentences 11 and 12 have the same entailments. In other words, they mutually entail each other.
Presupposition
A sentence is said to presuppose another if its truth and that of its negation both imply that the presupposed sentence is also true:
It is surprising that Peter passed the test
Pres: Peter passed the test.

It is not surprising that Peter passed the test
Pres: Peter passed the test
Pq
TT
FT
T or F?T

Difference between Entailment and Presupposition

Presupposition and entailment differ.
When a presupposing sentence is negated, the presupposition survives as in examples 19 and 20:
I regret studying law
Pres: I studied law
I do not regret studying law
Pres:I studied law

However, in entailment, negating the entailing sentence results in the failure of the entailment as in the following examples:
Peter is my brother (
I have a brother (entailment holds)
Peter is not my brother
I have a brother (we are not sure whether I have a brother or not hence entailment no longer holds )
Presupposition also holds in questioning, embedding with modals and in conditional clauses:
The king of France is bald
Pres: There is a King of France
Is the king of France bald
Pres: there is King of France
The King of France might be bald
Pres: There is a King of France
If the King of France is bald, then he should wear a hat
Pres: There is a King of France

Presupposition failure
Presupposition failure occurs when the proposition assumed to be true is in fact false. Different situations may be responsible for presupposition failure;
The use of a name or definite expression to refer when in reality the referent does not exist as in
29. P:The king of Moldova is highly respectable.

q:There is a king of Moldova.

The question is ‘is there a referent for the expression the King of Moldova? Is q true or false and if q is false, then what is the status of p?
Pq
TT
FT
T or F?T
?T v F ?F
The table above shows that if q is F then the status of p is questionable. This situation creates a truth value gap that results in presupposition failure.
That is, presupposition is inconsistent with actual sate of the world.

Failure to deny the presupposing proposition when negating the presupposition as in the following example:
P1:I’m going to talk about presupposition failure
q1:There is presupposition failure
p2:My claim is that there is no presupposition failure
q2: There is no presupposition failure
If p2 is true, then p1 is a presupposition failure. In this case, presupposition is not constant because both sentences affirm and deny the same proposition.
Thus the utterance lacks of constancy under negation.
Lack of clarity with respect to what is being presupposed:
31. A: Have you seen Mary
B: I think she just left the room
In 31 above the verb think presupposes that speaker b may or may not have seen Mary. Therefore it is not certain whether the speaker saw Mary or not.

Presupposition failure is only problematic for truth value semantics.
Presupposition: from Pragmatics perspective
*The pragmatic approach views presupposition as a resource for organising information for utmost clarity.
*Speakers usually order information through backgrounding and foregrounding, based on their estimation of their listeners’ knowledge:
32. p: John’s brother has come from Maun
q: John has a brother
There are two assertions in the above utterance:
a): John has a brother X
b): X has come from Maun
Assertion (a) is backgrounded in p because the information is contained within the NP John’s brother while assertion b is foregrounded because it is assigned the main verb in the sentence.
This shows that speakers usually decide what information to present first: old or new.
In this case, assertion b is the new information, and this is the reason it is foregrounded.
Also in presenting new information, speakers always have the opportunity to rank items based on what is considered important.

*The above explains why presupposition failure is not problematic when considered from the interactional approach.
*For example, the use of names and definite descriptions as referring expressions is governed by the accessibility of the referent to the listeners as in the following:
33. p: Maldova will arrive tomorrow.

q: Maldova exists.

34. p: The Mayor of the Village has died.

q: The village has a Mayor.
The interactional condition on referring demands that speakers’ use of a name or a definite description to refer as in 33 and 34 above implies that the listener can indeed identify the referent.
If a listener fails to identify a referent, a communication failure could occur but this could be rectified by seeking clarification (questioning).
Thus in pragmatics, presupposition is not considered from the narrow truth value perspective which depends on whether or not a referent exists.
In pragmatics, presupposition is considered from the more general view of the conditions governing the use of referring expressions. From the interactional perspective, presupposition can be defined as the set of assumptions made by participants in a conversation.

This set of assumptions referred to as common ground is context dependent. The assumptions are usually modified as new sentences are made which allows speakers to build new sentences on a common ground.
Where presuppositions are not necessarily known to a listener, such a situation is handled by the principle of accommodation:

35. p: My sister just had a baby
q: I have a sister
If q above is not known to the listener, then it accommodated as new information.
Lastly, presupposition in pragmatics is not treated as an independent entity.
This is because varied effects can be produced depending on the way syntactic structures and intonation patterns are used to show how new sentence fits into the background using notions of given and new information:
36: It rained on MONDAY (time is new information)
On Monday, it RAINED (even is new information)

Presupposition triggers:
A presupposition trigger is a construction or item that signals the existence of presupposition in an utterance. Such structures include:
Definite expressions:
p: John saw the man with two heads
q: There is a man with two heads
Cleft sentences or pseudo cleft sentence:
p: It was Henry that visited Rome
q: Someone visited Rome
p: What John lost was his notebook
q: John lost something
Lexical triggers such as factive verbs:
P: Mary realised that she was in debt
q: Mary was in debt
p: They both regretted eating the banana
q: They ate the banana
Change of state verbs
p: Have you started exercising regularly
q: you didn’t exercise