AbstractThis article uses a familiar and successful framework to organize and systematize the ethics of ecology and environmental science. Mid‐level principles have helped make the field of bioethics well understood and enabled it to influence laws, policies, and clinical decision‐making. We propose that a new set of principles could do the same for the larger field of environmental ethics. As was true with bioethics, the principles chosen need to already be well‐established. The insight is that to offer a complete analysis of a case or situation one must consider all of the principles. Thus one must choose a small set of mutually exclusive and jointly exhaustive principles. While there are thousands of articles using each of our principles, no one has identified them as a set of principles that can be easily taught and used to resolve dilemmas. Thus this article can help advance ecological and environmental ethics. Each of the four principles is briefly defined, and a little of their history and some current examples provided for each. The principles are: The Precautionary Principle, Biodiversity, Environmental Justice, and Sustainability. As a group they represent a complete picture of the ethical territory we must deal with in every value‐laden choice, clarifying why disagreements happen and what is at stake when trade‐offs must be made.