Fictionalism is the view that a serious intellectual inquiry need not aim at truth. It came to prominence in philosophy in 1980, when Hartry Field argued that mathematics does not have to be true to be good, and Bas van Fraassen argued that the aim of science is not truth but empirical adequacy. Both suggested that the acceptance of a mathematical or scientific theory need not involve belief in its content. Thus the distinctive commitment of fictionalism is that acceptance in a given domain of inquiry need not be truth-normed, and that the acceptance of a sentence from the associated region of discourse need not involve belief in its content. In metaphysics fictionalism is now widely regarded as an option worthy of serious consideration. This volume represents a major benchmark in the debate: it brings together an impressive international team of contributors, whose essays (all but one of them appearing here for the first time) represent the state of the art in various areas of metaphysical controversy, relating to language, mathematics, modality, truth, belief, ontology, and morality.