This book comprises four chapters, each of which examines public debt from a specific economic perspective. Chapter 1 studies potential fiscal externalities of the public debt in the framework of a monetary union. Chapter 2 examines the theoretical literature concerning how and if public debt impairs economic growth and finds no univocal and straightforward answer. Chapter 3 discusses the economic impact of the SARS-CoV-2 virus and addresses the question of whether limits to public debt ought to be respected or disregarded in the face of huge unemployment, collapsing tax revenues, and generous public expenditure programs. Lastly, Chapter 4 analyzes the response of central banks in emerging inflation targeting countries with floating exchange rates to changes in public debt.