The inherent complexity of environmental problems resonates throughout the creation and operation of environmental law. It shapes its structure and gives rise to questions that push the legal imagination of lawyers. ‘Environmental problems’ discusses the many types of environmental problems—from air pollution and wilderness destruction to waste dumping and climate change—and considers their common structure. It outlines the common structure of these problems and explains the finite capacity of the physical environment. Science has played a fundamental role in increasing our understanding of environmental problems, but it is also limited by the fact that in studying the environment we are studying large holistic systems in which there are multiple interconnected elements.