Studying humankind's relationship to the earth involves broad and deep questions for students as today's educators explore changing teaching methods. This article highlights benefits of a multidisciplinary approach to environmental education, drawing upon ancient natural philosophy as a coherent conceptual resource. The Greek philosopher Plotinus is introduced to show the application of ancient natural philosophy across all fields and on all levels of knowledge under a common banner. The significance of ancient natural philosophy is its conception of overall unity. This is the key. Unity is implicit in interrelationships between parts to whole on all levels of existence. From such a perspective, all life forms and other entities in the natural world can be understood as interrelated -- just as James Lovelock demonstrated in describing the "homeostatic" state of natural processes on earth. On a similar reasoning, the diversity in people, societies and places can be appreciated physically and sociologically as belonging to one world. Several studies are cited to explore this overlap between ancient natural philosophy and honouring the connection and dependence of humanity on the fragility of the earth's ecosystem.