This text is the last of a series of four volumes on environmental issues, particularly concerned with global problems, the available scientific information, which is necessarily incomplete, and the reasons of the policy makers. Ten authors contribute to six chapters. The first five deal with particular topics where some progress has been made with international agreement: the Law of the Sea, atmospheres and climate change, the ozone layer and - more all-embracing and elusive - sustainable development. The last chapter surveys the various participants in the complex political debates on these crucial questions, considers their various value positions and speculates on possible futures.