who worked at Helsinki and in various universities in the United States. While Hintikka wrote extensively on a variety of the great historical philosophers from Plato to Wittgenstein he is best-known for developments in formal semantics, particularly in its less usual applications, to deontic logic, the logic of question and answer, and intensional and epistemic logic. His leading analytical tool is that of a ‘model set’ known as a Hintikka set, or set of formulae constituting a consistent but partial description of a possible world. Works include Knowledge and Belief (1962), Models for Modalities (1969), Ludwig Wittgenstein, Half-truths and one and a half truths (1996), On Gödel (2000), and numerous edited volumes and collections.