The most important work by a key figure in German thought, Helmuth Plessner’s Levels of Organic Life and the Human, originally published in 1928, appears here for the first time in English, accompanied by a substantial Introduction by J. M. Bernstein, after having served for decades as an influence on thinkers as diverse as Merleau-Ponty, Peter Berger, Habermas, and the new naturalists.The Levels, as it has long been known, draws on phenomenological, biological, and social scientific sources as part of a systematic account of nature, life, and human existence.The book considers non-living nature, plants, non-human animals, and human beings in turn as a sequence of increasingly complex modes of boundary dynamics—simply put, interactions between a thing’s insides and surrounding world. On Plessner’s unique account, living things are classed and analyzed by their “positionality,” or orientation to and within an environment.“Life” is thereby phenomenologically defined, and its universal ye