The groundbreaking classic of twentieth-century German philosophy now available in English—with an introduction by J.M. Bernstein. Helmuth Plessner’s Levels of Organic Life and the Human, draws on phenomenological, biological, and social scientific sources to offer a systematic account of nature, life, and human existence. The book considers non-living nature, plants, non-human animals, and human beings a sequence of increasingly complex modes of boundary dynamics—simply put, interactions between a thing’s insides and the surrounding world. Living things are classed and analyzed by their “positionality,” or orientation to and within an environment. According to Plessner’s radical view, the human form of life is excentric—that is, the relation between body and environment is something to which humans themselves are positioned and can take a position. This “excentric positionality” enables human beings to take a stand outside the boundaries of their own body, a possibility with significant implications for knowledge, culture, religion, and technology. A powerful and sophisticated account of embodiment, the Levels shows, with reference both to science and to philosophy, how life can be seen on its own terms to establish its own boundaries, and how, from the standpoint of life, the human establishes itself in relation to the nonhuman. As such, the book is not merely a historical monument but a source for invigorating a range of vital current conversations around the animal, posthumanism, the material turn, and the biology and sociology of cognition.