Half a century ago, before the discovery of DNA, the Austrian physicist and philosopher Erwin Schrödinger inspired a generation of scientists by rephrasing the fascinating philosophical question: What is life? Using their expansive understanding of recent science to wonderful effect, acclaimed authors Lynn Margulis and Dorion Sagan revisit this timeless question in a fast-moving, wide-ranging narrative that combines rigorous science with philosophy, history, and poetry. The authors move deftly across a dazzling array of topics--from the dynamics of the bacterial realm, to the connection between sex and death, to theories of spirit and matter. They delve into the origins of life, offering the startling suggestion that life--not just human life--is free to act and has played an unexpectedly large part in its own evolution. Transcending the various formal concepts of life, this captivating book offers a unique overview of life's history, essences, and future. Supplementing the text are stunning illustrations that range from the smallest known organism (Mycoplasma bacteria) to the largest (the biosphere itself). Creatures both strange and familiar enhance the pages of What Is Life? Their existence prompts readers to reconsider preconceptions not only about life but also about their own part in it.