This casual and lively book deals with some of the most basic philosophical questions we have: why are we here? How did life arise from nonliving particles? What is the fate of the earth? Sagan (What Is Life?), son of astronomer and science writer Carl Sagan, draws on, among others, science, philosophy and the speculations of science fiction in attempting to answer these questions. He begins with a quick introduction to James Lovelock's Gaia hypothesis, that the Earth is a living, self-regulating organism, and that life is not just a passenger on Earth but an integral part of the planet's systems.