Hans Jonas’ thinking, especially his philosophical biology, deals indirectly with the ontological relationship between human beings and animals. In this respect, he rejects both dualistic and monistic approaches to the problem. Thanks to the “ontological revolution” testified by the phenomenon of life, Jonas is able to trace a scala naturae of growing complexity. More specifically, several species of animals present “trans-animal potentialities”, which represent a biological and ontological link with the human being. The animal is somehow able to prefigure the human form of life. However, according to Jonas, the existence of a “metaphysical gap” between human being and animal is evident. The human uniqueness consists in its capacity of being responsible and in preserving the overall conditions for an authentic future life.