Hans Jonas (1903–1993) was one of the most important German-Jewish philosophers of the 20th century. A student of Martin Heidegger and close friend of Hannah Arendt, Jonas advanced the fields of phenomenology and practical ethics in ways that are just beginning to be appreciated in the English-speaking world. Drawing here on unpublished and newly translated material, Lewis Coyne brings together for the first time in English Jonas's philosophy of life, ethic of responsibility, political theory, philosophy of technology and bioethics. In Hans Jonas: Life, Technology and the Horizons of Responsibility, Coyne argues that the aim of Jonas's philosophy is to confront three critical issues inherent to modernity: nihilism, the ecological crisis and the transhumanist drive to biotechnologically enhance human beings. While these might at first appear disparate, for Jonas all follow from the materialist turn taken by Western thought from the 17th century onwards, and he therefore seeks to tackle all three issues at their collective point of origin. This book explores how Jonas develops a new categorical imperative of responsibility on the basis of an ontology that does justice to the purposefulness and dignity of life: to act in a way that does not compromise the future of humanity on earth. Reflecting on this, as we face a potential future of ecological and societal collapse, Coyne forcefully demonstrates the urgency of Jonas's demand that humanity accept its newfound responsibility as the 'shepherd of beings'.