This book offers a compelling exploration of Hans Jonass philosophical legacy, focusing on the intertwined concepts of freedom and responsibility in relation to nature, ethics, and technology. Drawing on Jonass postWorld War II writings, Angela Michelis traces his intellectual evolution from early studies of Gnosticism to his groundbreaking work in the philosophy of biology and ethics. The book presents Jonass dynamic conception of organic life and outlines his principle of responsibility as a planetary ethic for the age of ecological crisis. Combining biographical insightbased on exclusive interviews with Jonass wife Lorewith rigorous philosophical analysis, Michelis situates Jonass thought within contemporary debates on sustainability, anthropocentrism, and the moral obligations of humanity. This timely volume reaffirms Jonass relevance for todays urgent ethical challenges and serves as a valuable resource for scholars and students in philosophy, environmental studies, and bioethics.