Yellowstone National Parks mission and policy can be clarified by analysis of the natural and the unnatural. Nature is a comprehensive word, in some uses excluding nothing; more useful is a contrast distinguishing nature and culture. Specifying "wild nature" denotes spontaneous nature absent human influence. Critics claim that the meaning of wild nature, especially of wilderness, is a foil of culture. Pristine nature, often romanticized, is contrasted with a technological and industrial culture. By this account, wilderness is a social construction.

Nevertheless, wild nature successfully denotes, outside culture, an evolutionary and ecological natural history, which remains present on the Yellowstone landscape, jeopardized by numerous human influences, including the invasions of exotic species. Natural processes have returned in the past, as when Native Americans left the landscape. Natural processes can be preserved today, because of, rather than in spite of, park management. Over much of the North American landscape nature is managed and at an end. Yellowstone provides an opportunity to encounter and to conserve "untrammeled" nature as an end in itself, past, present, and future.