This book provides a summary of the main concepts involved in environmental ethics, sustainability and decisions and a consistent sequence of environmental ethics, sustainability and decisions. It presents many environmental ethics, by focusing on maximising welfare within teleological approaches and minimising inequalities within deontological approaches. It presents many sustainability paradigms, by focusing on weak sustainability to maximise welfare and strong sustainability to minimise inequalities. Two main decisions are presented by focusing on policies (taxes, standards, subsidies, permits, protected areas, exploitation rights) and projects (CBA) towards efficiency to maximise welfare and policies (national laws/regulations, bilateral/multilateral agreements) and projects (MCA) towards equity to minimise inequalities.