This book consists of an introduction and eleven essays written by Professor Hintikka approximately between 1970 and 1975. All but one of the essays is published in some form elsewhere. But more than most such collections, this one has a measure of unity and continuity. All the essays involve applications of Hintikka's semantical approach to epistemic notions. And although the book contains few major alterations in Hintikka's previously published views, readind the essays from first to last provides a good overall picture of his philosophical stance in this area. Read this way, the book does have limitations. Several of the articles largely elaborate on viewpoints more fully stated in earlier work (especially in “Semantics for Propositional Attitudes”, “Existential Presuppositions and Uniqueness Presupposions”, and “On the Logic of Perception” – all collected in Hintikka's earlier Models for the Modalities).