"Realism, Mathematics and Modality" presents the work of Hartry Filed, described as one of the world's most influential philosophers of mathematics, and combines central papers in that area (two of them rewritten for this volume) with a new overview, an essay on the philosophy of space and time and new postscripts. The overriding concern of most of the essays is with the development of a satisfactory fictionalist account of mathematics. Hartry Field develops and defends an anti-Platonist philosophy of mathematics, one on which mathematics need not be true, but instead must be "conservative" and dispensable in applications. In defending its dispensability, Field is led to defend a substantivalist view of space-time and to reassess prevailing views about modality. He thus gives expression in one volume to an intensive and concerted philosophical enterprise.