In this article, I analyze the onto-ethical basis of the Jonasian concept of “solidarity of interests”, understood as a link uniting all living beings in a network of existential interdependence. This perspective reinforces the contemporary critique in ethics and science of anthropocentrism which is, in the same way, at the heart of Hans Jonas’ critique of traditional ethics and modern science. This article analyzes the onto-ethical bases of this concept with the help of the “principle of mediacy” that Jonas understands as the capacity to establish mediations with the environment in view not only of the preservation of the other, but also of oneself, in such a way that it would be a very particular kind of solidarity, the one that, in the organic framework, does not exclude the interest of life for self-preservation. Solidarity is an ontological condition of interdependence between beings and also, according to Jonas, between things, including a sharing of identity between different forms of life and a fundamental mark of Being, because, according to this logic, the most intimate experience of life is to resist death – indeed, it is this solidarity that becomes the main motive of such relationships. Within the history of solidarity networks, the human being occupies a particular place: either it is in him that precariousness assumes more obvious versions; or it is in him that, as a response, capacities more favorable to his subsistence are developed. This concept of solidarity becomes central to understanding the degrees of freedom that characterize life with respect to the ethical obligation to preserve them through the principle of responsibility. In other words, solidarity must also be the basis of responsibility: it is a question of thinking about the affirmation of life within the collective framework of guarantees concerning the conditions of existence at the present moment and especially those concerning the future.