This volume was prepared for two reasons. First, the essays are offered as tokens of affection and esteem for Sir Robert Jennings by some of his many friends and colleagues; and his recent eightieth birthday and Presidency of the Court provided an appropriate opportunity. We are only sorry that it was not possible to publish a larger volume, to accommodate the many others who would have wished to contribute to this work. Second, the International Court of Justice is approaching its first half-century, and the time seemed ripe for reflection upon its work. The contributors co-operated in preparing what is less of a traditional Festschrift than a set of chapters which together cover the main areas of the Court's work. We are grateful to them for their efforts, and for the willingness with which they accepted the constraints that the co-ordination of the subject matter of their essays necessitated.