This volume of essays is dedicated to the memory of John McMahon. It is a tribute by his friends and by Chatham House, for which, when he died in April 1969, he was writing a major work on decision-making in the UN specialized agencies. The volume contains a study by him of the judicial methods of the European Communities Court, which was one of the steps towards the larger work. The other essays all have themes that were close to the interest and work of John McMahon, and the volume is offered as a token of the book that was not to be finished. Contributors include: P. J. Allott, Ian Brownlie, Rosalyn Higgins, Oscar Schachter, S. A. de Smith, Andreas J. Jacovides and Michael Hardy.