On Presupposition and Entailment

利红

1.Presuppostition

1.1 The definition of presupposition

The widely-studied subject in linguistic-presupposition has originated from philosophy field， in which the philosophers used this concept for the research of the phenomena of projection and the words of reference in natural language. In Pragmatics， George Yule （2000） said that a presupposition is something the speaker assumes to be the case prior to making an utterance. In another words， a presupposition is a proposition which is assumed to be true in advance when the speaker makes an utterance. Though the sentence is negated， the presupposition remains true.

1.2 Types of presupposition

（1）Semantic presupposition and pragmatic presupposition.Some linguists divide presupposition into two types， namely semantic presupposition and pragmatic presupposition， which was first proposed by the French linguist， Keenan （1983）. Semantic presupposition focuses on the relationship between propositions and the project relationship of truth value condition. Semantic presupposition is an essential property of semantic relationship of interior language， so it is unchangeable and can not be influenced by other factors. Pragmatic presupposition is the premise that makes the speech act come true and it comes into being under the interference of speech activities. Pragmatic presupposition draws its attention on the relation of the langue symbol， the symbol users and the context. Pragmatic presupposition is always restricted by the context and the cognitive experience and has a close relation with the speakers， both sides of the speech activity and the factors outside the speech.

（2） Concrete classification of presupposition.In recent years， the pure semantic presupposition， which is not influenced by the factors outside of the speech， can hardly explain those complicated linguistic phenomena in real life， but the development of pragmatics exactly provides a new bright prospect of presupposition. George Yule （2000） has divided presupposition into seven types in his book Pragmatics： potential presupposition， existential presupposition， factive presupposition， non-factive presupposition， lexical presupposition， structural presupposition and counterfactual presupposition.

2. Entailment

2.1 The definition of entailment

Whats called entailment is a sense relation between sentences as following： Under all circumstance， if P is true and Q is also true， then P entails Q （P||-Q）. Namely， if P is true， Q will also be true； if Q is not true， P will not be true， too； but if Q is true， P will not be necessarily true.

The member sentences of each pair are in such a relationship that the truth of the second sentence necessarily follows from the truth of the first sentence， while the falsity of the first follows from the falsity of the second. In terms of semantic components， we can say it is because （a） sentences contain words which have all the semantic components of a word used in （b） sentences.

2.2 Types of entailment

There are two ways to classify the entailment as follows：（1） According to the semantic relation of the propositions， entailment can be divided into three types： ①Antithetic relation；②Comparative relation；③Inclusive relation.（2） According to the structure， entailment can be divided into two types： nominal entailment and explanatory entailment.

3. The analysis of presupposition and entailment

3.1 The commonnesses of presupposition and entailment

Comparing presupposition with entailment， in spite of the difference， we can get some commonnesses of them. Both presupposition and entailment refer to the meaning relations between the truth value and the preposition conveyed by the sentence. Both of them are the information that are not stated but communicated. They are both indications inferred from the meaning of the sentence in itself， whose objective is to make research on the influence made by other factors outside of the sentence.

3.2 The differences between presupposition and entailment

① In general， presupposition only involves the nominal composition in the sentence， while entailment involves the whole stated proposition. ② The relation of truth value that the analysis of entailment is associated with is a kind of deduction， and is limited in this deduction. However， presupposition is established above the deduction， and in another aspect （also the most important one）， it needs the validation of the context to make up the deficiency. In another word， the analysis of entailment is static， while that of presupposition is combinedly dynamic and static. The analysis of presupposition is mainly dynamic and the object of the research should be the embodied sentence （contextual sentence）. ③Presupposition is changeable in semantics and is influended by the context or the factors outside of the sentence， it is defeasible. However， entailment is a purely logic reasoning and is an inherent property on its own， so it is undefeasible. The defeasibility of presupposition can show in following two aspects. ④From the theory of conversational implicature of Grice， we get to know that entailment just convey partial information， while presupposition deliver the background information. ⑤ Speakers but sentences have presuppositions while sentences but speakers have entailment.