Modal Logic, originally conceived as the logic of necessity and possibility, has developed into a powerful mathematical and computational discipline. It is the main source of formal languages aimed at analyzing complex notions such as common knowledge and formal provability. Modal and modal-like languages also provide us with families of restricted description languages for relational and topological structures; they are being used in many disciplines, ranging from artificial intelligence, computer science and mathematics via natural language syntax and semantics to philosophy.
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The present anthology has its origin in two international conferences that were arranged at Uppsala University in August 2004: "Logicism, Intuitionism and F- malism: What has become of them?" followed by "Symposium on Constructive Mathematics." The rst conference concerned the three major programmes in the foundations of mathematics during the classical period from Frege's Begrif- schrift in 1879 to the publication of Godel' ] s two incompleteness theorems in 1931: The logicism of Frege, Russell and Whitehead, the intuitionism of Brouwer, and Hilbert's formalist and proof-theoretic programme....

The essays in this collection are written by students, colleagues, and friends of Nuel Belnap to honor him on his sixtieth birthday. Our original plan was to include pieces from fonner students only, but we have deviated from this ever so slightly for a variety of personal and practical reasons. Belnap's research accomplishments are numerous and well known: He has founded (together with Alan Ross Anderson) a whole branch of logic known as "relevance logic." He has made contributions of fundamental importance to the logic of questions. His work in modal logic, fonnal pragmatics, and the theory...