Book excerpt: The concept of ‘the triple bottom line’ has recently emerged to describe a new framework for development aimed at achieving economic and social balance while maintaining the long-term integrity of ecological systems. This requires measuring not only the economic viability of projects, but also their impact on the environment and their contribution to society. We live in a world where most people are aware of the importance of our environment. The way in which this realisation came about has, in hindsight, not been as simple as could have been expected. Systematic evaluations of the economic viability of projects using discounting date back to the beginning of the last century and are something which has been readily accepted, especially over the last few decades. However, an integrated approach, including environmental and social aspects, is much more recent, and even now, the methods and methodologies for such an approach are still being developed. This volume details the state of the art of the development towards the triple bottom line. It indicates where there is still debate about fundamental principles, where theory has been overlooked in the name of convenience, and where there are still unresolved problems. The discussions provided here will serve to provide a more detailed understanding of what we do in our calculations, what they mean and the limitations thereof.