Jaakko Hintikka

Works

• 1962Knowledge and Belief: An Introduction to the Logic of the Two Notions

  Treats “a knows that p” and “a believes that p” as operators interpreted over the possible worlds compatible with what a person knows or believes, and so founded epistemic logic.

• 1973Logic, Language-Games and Information

  Essays developing game-theoretical semantics: the meaning of quantifiers is explained by games of seeking and finding between a verifier and a falsifier, an idea Hintikka linked to Wittgenstein’s language-games.

Position

Hintikka is on the map as the founder of epistemic logic and an influential logician of the twentieth century. In “Knowledge and Belief” (1962) he treated “a knows that p” and “a believes that p” as modal operators: to know something is to exclude all possibilities incompatible with it, so the logic of knowledge can be studied with the possible-worlds methods then being developed. The book opened a field that later reached computer science and economics. From the late 1960s he developed game-theoretical semantics: the truth of a sentence is defined by a game between a verifier and a falsifier, in which, for example, the verifier chooses an object for an existential quantifier; the sentence is true if the verifier has a winning strategy. He linked this idea to Wittgenstein’s language-games and later built on it an “independence-friendly logic”, with which he challenged received views of first-order logic and of the foundations of mathematics. He also proposed an interrogative model of inquiry, in which science proceeds by putting questions to nature, and wrote influential interpretations of Aristotle, of Descartes’ cogito as a performance rather than an inference, of Kant and of Wittgenstein.

Life & context

Jaakko Hintikka was born on 12 January 1929 in Vantaa near Helsinki. He studied mathematics and philosophy at the University of Helsinki and took his doctorate in 1953 under Georg Henrik von Wright with a thesis on distributive normal forms. After three years as a junior fellow at Harvard (1956–59) he became professor of practical philosophy in Helsinki (1959–70). He later held research posts at the Academy of Finland and professorships at Stanford (part-time from 1964), Florida State University (1978–90) and Boston University (from 1990). For decades he edited the journal Synthese, and in 2005 he received the Rolf Schock Prize in logic and philosophy. He died in Porvoo on 12 August 2015.

Further main works

• Cogito, ergo sum: Inference or Performance? (Philosophical Review 71, 1962)
• Time and Necessity: Studies in Aristotle’s Theory of Modality (1973)
• Investigating Wittgenstein (with M. B. Hintikka, 1986)
• The Principles of Mathematics Revisited (1996)