Technological progress carries the risk of wiping out humanity or of changing it fundamentally. High-risk technologies (nuclear power, genetic engineering, artificial intelligence) are not only profitable, but in the worst-case scenario they also pose an existential threat to humanity and to non-human nature. The philosopher Hans Jonas (1903–1993) saw this in the 1970s and urged caution. He developed an ethic for technological civilization that is still debated today. With his book Das Prinzip Verantwortung (The Imperative of Responsibility), Jonas has remained one of the most influential philosophical critics of technology. This article, which is written particularly for those who do not yet know his work, aims to introduce his complex and metaphysically founded ethics – an ethical approach that has not lost any of its relevance.