In the this article I try to show how an interaction between the phenomenological works of Enzo Paci and of Bernhard Waldenfels can lead to some interesting results concerning Husserl's search for a rigorous and apodictic ground for knowledge and for a universal science which involves the whole life of consciousness also in its intersubjective aspects. I do not try to compare the two thinkers, nor to assess the correctness of their interpretation of Husserl's thought, but to show through their thoughts some remarks concerning problems which are still crucial in the philosophical and phenomenological debate. Paci's insistence on the practical and existential value of phenomenological reflection leads to constantly have to face the question “what is to be done?”, demanding in this way for an answering to the provocation of the Alien so well analysed by Waldenfels. Through such a process a common constitution does preserve from the lost of diversity and, at the same time, does not escape responsibility.
