These essays focus on central concerns of contemporary metaphysics and the growing interest in ontological issues.What is it for an object to persist through time? What is the relation between an object and its parts? Do we need an ontology of truth-makers? These questions reflect the central concerns of contemporary metaphysics and are the focus of the essays published within this volume.What is it for an object to persist through time? What is the relation between an object and its parts? Do we need an ontology of truth-makers? These questions reflect the central concerns of contemporary metaphysics and are the focus of the essays published within this volume.What is it for an object to persist through time? Do things have essences? What is the relation between an object and its parts? Are objects more real than their parts, or vice versa? Could there be spatio-temporally coincident objects? Do we need an ontology of truth-makers? These interrelated questions reflect the central concerns of contemporary metaphysics, which in recent years has seen an intensification of interest in ontological issues. They are the focus of the essays collected in this volume, which arose from the Being: Developments in Contemporary Metaphysics conference held at the University of Leeds in September, 2006.Preface; Notes on contributors; 1. In defence of three-dimensionalism Kit Fine; 2. Modes of extension: comments on Kit Fine's 'In defence of three-dimensionalism' Peter Simons; 3. Two notions of being: entity and essence E. J. Lowe; 4. Essence and being Scott A. Shalkowski; 5. Micro-composition D. H. Mellor; 6. Working parts: reply to Mellor J. Robert G. Williams; 7. Truthmakers, realism and ontology Ross P. Cameron; 8. Monism and statespace structure Theodore Sider; 9. Coincidence and identity Penelope Mackie; 10. Nihilism without self-contradiction David Liggins; 11. Persistence and determination Katherine Hawley.