title: Defining 'life'.
abstract: There is no broadly accepted definition of 'life.' Suggested definitions face problems, often in the form of robust counter-examples. Here we use insights from philosophical investigations into language to argue that defining 'life' currently poses a dilemma analogous to that faced by those hoping to define 'water' before the existence of molecular theory. In the absence of an analogous theory of the nature of living systems, interminable controversy over the definition of life is inescapable.
authors.affiliation: Department of Philosophy and the Center for Astrobiology, University of Colorado, Boulder, CO 80309, USA.
authors.forename: Carol E
authors.initials: CE
authors.lastname: Cleland
authors.forename: Christopher F
authors.initials: CF
authors.lastname: Chyba
mesh_terms: D019418:Evolution, Chemical; D018559:Exobiology; D005118:Extraterrestrial Environment; D019369:Life; D000069497:Origin of Life; D010684:Philosophy; D014867:Water
chemical_list: D014867:Water