SOPhiA 2018

Salzburgiense Concilium Omnibus Philosophis Analyticis

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Programme - Talk

Tarski's Definition of Logical Consequence: Why Etchemendy's Criticism is Based on False Assumptions
(Logic, English)

What does it mean that a sentence A is a logical consequence of a set of sentences B? What are the essential characteristics by which a valid argument can be distinguished from an invalid one? In his 1936 paper ``On the Concept of Logical Consequence'' Tarski answered these questions by giving precise definition of the notion of logical consequence; according to this definition, a sentence A is a logical consequence of a set of sentences B iff every interpretation that makes all sentences of B true also makes A true. In other words: A sentence A is a logical consequence of a set of sentences B iff every model of B is a model of A. Likewise, a sentence A is logically true iff A is true in every interpretation, i.e. iff every model of the empty set of formulae is also a model of A.

Even though this definition of logical consequence proved to be very fruitful, in his book ``The Concept of Logical Consequence'' Etchemendy claims that Tarski's definition of logical consequence is flawed. He concludes that Tarski's account is not to be seen as an adequate definition of the notion of logical consequence, neither conceptually nor extensionally, since -- as he points out -- Tarski's definition does not capture the essential features of logical consequence and therefore leads to wrong results. In my talk I will not be able to discuss the whole book, so I will mainly focus on Etchemendy's epistemological argument and on the counterexamples he offers in order to show that Tarski's account fails extensionally.

My talk consists of three parts: In the first part I will explain Tarski's definition of logical consequence. In the second part I will present Etchemendy's epistemological argument and his counterexamples against Tarski's definition. Finally, I want to argue that Etchemendy's criticism on Tarski's account is based on a misinterpretation of this account and a misunderstanding of his aims.


Chair: Stefan Forster
Time: 12:00-12:30, 14 September 2018 (Friday)
Location: SR 1.006

Shota Uka 
(University of Salzburg, Austria)

After finishing her B.A. in Philosophy at the University of Graz (Austria) in 2016, Shota Uka joined the master's programme in Philosophy at the University of Salzburg (Austria) in order to focus on analytic philosophy. Currently she is working on her master thesis, discussing Tarski's definition of logical consequence. She is mainly interested in logic, philosophy of logic and mathematics, and also philosophy of language.

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