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In the TE framework, the entailing and entailed texts are termed text (t) and hypothesis (h), respectively.Textual entailment is not the same as pure logical entailment – it has a more relaxed definition: "t entails h" (t ⇒ h) if, typically, a human reading t would infer that h is most likely true. [1]
The Polish logician Alfred Tarski identified three features of an adequate characterization of entailment: (1) The logical consequence relation relies on the logical form of the sentences: (2) The relation is a priori, i.e., it can be determined with or without regard to empirical evidence (sense experience); and (3) The logical consequence ...
As the best known of the paradoxes, and most formally simple, the paradox of entailment makes the best introduction. In natural language, an instance of the paradox of entailment arises: It is raining. And It is not raining. Therefore George Washington is made of rakes.
Entailment contrasts with the pragmatic notion of implicature. While implicatures are fallible inferences, entailments are enforced by lexical meanings plus the laws of logic. [ 3 ] Entailments also differ from presuppositions , whose truth is taken for granted.
A definition that provides a means for replacing each occurrence of the definiendum with an appropriate instance of the definiens. [131] [132] Contrast implicit definition. explosion The principle in logic that from a contradiction, any statement can be proven, related to the principle of ex falso quodlibet. exportation
Strawson entailment has played an important role in semantic theory since some natural language expressions have been argued to be sensitive to Strawson-entailment rather than pure entailment. For instance, the textbook theory of weak negative polarity items holds that they are licensed only in Strawson- downward entailing environments.
In classical logic, intuitionistic logic, and similar logical systems, the principle of explosion [a] [b] is the law according to which any statement can be proven from a contradiction. [1] [2] [3] That is, from a contradiction, any proposition (including its negation) can be inferred; this is known as deductive explosion. [4] [5]
The definition of tautology can be extended to sentences in predicate logic, which may contain quantifiers—a feature absent from sentences of propositional logic. Indeed, in propositional logic, there is no distinction between a tautology and a logically valid formula. In the context of predicate logic, many authors define a tautology to be a ...