This Chapter explores the development of Jonas’s key concepts—freedom, identity, and responsibility, focusing on the pivotal transition from his early studies of gnosticism to his work on the philosophy of biology. I identify a crucial element of continuity in Jonas’s thinking: the relationship between humanity and the world. This idea of a “shared nature,” in fact, is a central theme in Jonas’s intellectual journey, forming the basis for his reflections on living organisms, which culminate in his best-known works. Jonas challenges both Darwinian evolutionary theory and the materialistic views dominant in the natural sciences, proposing a dynamic conception of organic nature that includes a spiritual element. In this framework, metabolism is the first form of freedom within nature itself, orienting it teleologically toward the preservation of life.