A Study Of Lewis' S Anti - Factual Conditional Sentence

David Lewis (1940-2001) who was born in Oberlin of Ohio is professor ofphilosophy at Princeton University. In this thesis, we mainly introduce the theory ofcounterfactual conditionals of David Lewis.This thesis is divided into four chapters. The chapter1is mental source ofcounterfactual conditionals of David Lewis. The counterfactual conditionals exist astwo approaches: road of possible world and road of linguistics. The former was firstput forward by William Todd and developed by Stalnaker and David Lewis. The mainideas of this approach are by means of possible world concept to explain conditionals.The chapter2introduces Lewis’s an analysis of counterfactuals. Lewis shallintroduce a pair of counterfactual conditional operators intended to correspond to thevarious counterfactual conditional construction of ordinary language, and he shallinterpret these operators by saying how the truth value at a given counterfactualconditional. Lewis’s interpretation of the‘would’ counterfactual as a variably strictconditional, together with his definition of the ‘might’ counterfactual in terms of the‘would’ counterfactual, yield derived truth conditions for the ‘might’ counterfactual.The chapter3expounds the main content of Lewis’s counterfactual conditionals.Impossible antecedents and true antecedents: Lewis pointed out that a counterfactualwith true antecedents is true if and only if the consequent is truth. In short,counterfactuals with true antecedents reduce to material conditionals. Counterfactualfallacies and potentialities: counterfactual fallacies mainly include the fallacy ofstrengthening the antecedents, the fallacy of transitivity, and the fallacy ofcontraposition. Possible worlds: Lewis believes that there are possible worlds otherthan the one we happen to inhabit and possible worlds are entities which areindependent of our real world.The chapter4is the reflection to the theory of counterfactual conditionals ofDavid Lewis. The counterfactual conditionals of David Lewis have its values, but stillhave its limitation. The limitation is that ambiguity of counterfactual conditionals makes David Lewis’s ideal reduce a theory that provide Joint similarity. Its value isthat David Lewis opens up the possible world semantics to study counterfactualconditionals method, which make a great contribution for conditional logic. Therefore,although the counterfactual conditionals of David Lewis have its limitation, its valueis much greater than limitation.