ABSTRACT
Sustainability does not refer only to the state of the environment. It has come to refer to the state of human life on the planet as well. The health of the global society can be assessed in systemic terms such as poverty or inequality, or individual measures such as mental health or obesity. On these and other measures, Earth is not doing well. Over 80 percent of the global population lives in poverty, on less than US$10 per day. In practical terms, sustainability refers to some condition that is to be maintained over a prolonged period. Surely, we do not mean to maintain the present levels of human suffering and environmental breakdown.
