Provides an overview of the main ideas of Laudato Si', arguing that it lays down a durable moral foundation for the transformative sustainable development agenda endorsed by 193 countries in 2015. The first chapter is a short introduction: explaining the nature of a papal encyclical, situating it in the corpus of Catholic social teaching, and highlighting the direct relevance of Laudato Si' to the social, economic and environmental challenges of our day. The second chapter discusses the nature of the social and environmental problems, touching on issues like climate change, loss of biodiversity, as well as rising inequality and social exclusion. The third chapter provides the main theological arguments (stated in layman's terms) for protecting our common home. It also introduces the core idea of Laudato Si': integral ecology. The fourth chapter turns its attention to the human roots of the crisis, and explores the problems with individualism and excess reliance on a technocratic paradigm. It also discusses the role and limitations of markets, and lays out the responsibility of the business sector. The fifth chapter addresses political solutions at the global, national and local levels.