The English School (ES) is an approach to International Relations (IR) that posits that the relationships between states and other significant actors take place in a social setting. This social setting consists of a complex web of rules, principles, practices, and institutions, the identification and analysis of which is a necessary first step to the understanding of ‘how things work’ internationally. As an approach to IR the ES has been influenced by classical Realism and shares common ground with Constructivism and liberal approaches such as Regime Theory. But it continues to set out a distinctive position, both methodologically and substantively, defining itself against these and other approaches. It has its roots in the teaching of C. A. W. Manning at LSE in the 1930s and 1940s and his explorations of the concept of international society. Later scholars traced its roots further back in time in the classical political thought of Grotius, Suarez, Gentili, Vattel and other notable jurists and politico-legal theorists of early-modern Europe. It began to take shape through the work of the British Committee on International Theory in the 1950s and 1960s and acquired international standing in the decades that followed through the widely cited and influential writings of Martin Wight and Hedley Bull. Today it is a body of theory with a growing number of adherents across the world, a strong presence at international conferences, and a steady output of scholarly publications.