Early in his career, he devised a
semantics of modal logic essentially analogous to
Saul Kripke's
frame semantics, and discovered the now widely taught
semantic tableau independently of
Evert Willem Beth. Later, he worked mainly on
game semantics, and on
independence-friendly logic, known for its "
branching quantifiers", which he believed do better justice to our intuitions about
quantifiers than does conventional
first-order logic. He did important exegetical work on
Aristotle,
Immanuel Kant,
Ludwig Wittgenstein, and
Charles Sanders Peirce. Hintikka's work can be seen as a continuation of the analytic tendency in philosophy founded by
Franz Brentano and Peirce, advanced by
Gottlob Frege and
Bertrand Russell, and continued by
Rudolf Carnap,
Willard Van Orman Quine, and by Hintikka's teacher
Georg Henrik von Wright. In 1998, for instance, he wrote
The Principles of Mathematics Revisited, which takes an exploratory stance comparable to that Russell adopted in his
The Principles of Mathematics in 1903. ==Selected books==