This book attempts to provide an ethical foundation with which to address the question, 'Should we spread life beyond Earth?' It examines the material conditions of the solar system, the limits of consciousness, the limits of society, and the long term possibilities of sending human life out into the universe. The author delineates the ethical criteria of sentient life and considers justifications of space travel for the purpose of human expansion. Duemler gives special attention to the utilitarian explanation which concludes that if life did [gnyad throughout the solar system, or even the galaxy, then this would serve to increase the amount of sentient life and, if life in the new world is a balanced positive, is therefore a positive event. Three main issues, drawing upon both science and philosophy, fall at the center of the discussion: supporting evidence not based on questionable dogma nor requiring huge intuitive leaps of faith; it must square with natural selection and have biological plausibility; and it must have inherent value, not requiring underlying conditions for a judgement to pass.