When philosophers participate in the interdisciplinary ethical, environmental, economic, legal, and social analysis of nanotechnologies, what is their specific contribution? At first glance, the contribution of philosophy appears to be a clarification of the various moral and ethical arguments that are commonly presented in philosophical discussion. But if this is the only contribution of philosophy, then it can offer no more than a stalemate position, in which each moral and ethical argument nullifies all the others. To provide an alternative, we must analyze the reasons behind the prevailing individual and cultural relativism in ethics. The epistemological investigation of this stalemate position will guide us to the core problem of the relation between theory and action (“Part 1: From a conceptual to a speech act analysis of moral arguments”). The stalemate can be overcome from a pragmatic philosophical standpoint, which combines epistemology, philosophy of language—that is, the philosophy of speech acts—and practical reasoning—that is, reasoning about decision-making (“Part 2: Moral argumentation from a pragmatist perspective”). From this philosophical standpoint, it will be possible to show how philosophy can accompany and support the development of nanotechnologies (“Part 3: Philosophy and the evaluation of the development of nanotechnologies”).