As a distinct biological subdiscipline, ecology did not emerge until the twentieth century. But its underlying conceptual framework was developed long before. Important organizing ideas grew out of the eighteenth-century physico-theological tradition, for example with Carl Linnaeus’s concept of an “economy of nature” or the related idea of an interconnecting “nexus” between organisms of different species. In the final years of his life, Immanuel Kant elaborates on these ideas and formulates concise descriptions and conceptual models for them. Kant’s underlying thought applies his concept of a “natural purpose” to the interaction of organisms from different species, thus arriving at a second-order organization of nature, the “organizing of systems of organized bodies” as he calls it. My contribution analyzes Kant’s almost entirely neglected proto-ecological ideas in their historical context.