Alfred Tarski

Alfred Tarski (1901–1983) was a Polish-American logician and mathematician whose work shaped model theory, formal theories of truth, and algebraic logic.

First-order logic: A formal system that represents objects, properties, and relations using quantifiers and predicates. Its languages and structures provide the setting for Tarski’s accounts of truth and logical consequence.
T-schema: A pattern linking a sentence’s truth to the condition that the sentence itself holds. Tarski used instances of this pattern to state adequacy conditions for formal truth definitions.
Warsaw School of Mathematics: A major Polish mathematical community centered in Warsaw during the first half of the twentieth century. Tarski’s early work grew within the city’s unusually active mathematical institutions.
Jan Łukasiewicz: A Polish logician known for work on many-valued logic and Polish notation. He was a leading figure in Warsaw logic during Tarski’s formative years.
Tarski's decision method: A quantifier-elimination procedure for deciding sentences in elementary algebra and geometry over real numbers. It turned a semantic insight into an algorithm for a substantial class of mathematical questions.
Model theory: The study of relationships between formal languages and the mathematical structures that satisfy their sentences. Tarski established core methods and results that helped make this field a distinct discipline.
Tarskian definition of truth: A recursive definition that specifies truth for a formal language relative to an interpretation. It defines truth through the structure of sentences rather than through an unrestricted truth predicate.
Lwów–Warsaw School: A Polish philosophical and logical movement known for rigorous analysis and formal methods. Its standards of precision shaped the intellectual culture in which Tarski began his career.
Stanisław Leśniewski: A Polish logician who developed the systems of protothetic, ontology, and mereology. Tarski studied with him and worked within the distinctive formal tradition he created.
Quantifier elimination: A procedure that replaces formulas with quantified variables by equivalent formulas without those quantifiers. Tarski’s method for real closed fields became a landmark example of its power.

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