Biology occupies a position among the sciences at once marginal and central. Marginal because-the living world constituting but a tiny and very "special" part of the universe-it does not seem likely that the study of living beings will ever uncover general laws applicable outside the biosphere. But if the ultimate aim of the whole of science is indeed, as I believe, to clarify man's relationship to the universe, then biology must be accorded a central position . . .