The article considers the questions posed by environmental ethics in the light of the work of Hans Jonas, especially his work Das Prinzip Verantwortung. Jonas centers his ethic on the concept of responsibility, which finds its expression in the categorical imperative that enjoins us to take into account the future effects of our actions. The specification of this imperative generates a series of problems: 1) given that the specification rests on complex causal chains, it has an hypothetical character; 2) the (...) effects that are the object of imperatives are external to our intentions (externality); 3) the complexity of the causal chains involved generates threshold effects; 4) the complexity of the causal chains prevents us from having a complete knowledge of it. The author then considers the possibilities and limits of Jonas' ethics to solve these problems. (shrink)