Uncertainty replaces the conviction that rationality may be founded, ultimately. Comments on and exemplified by Zygmunt Bauman's "Intimations of postmodernity" (1992), the Quality-of-life discussion (Nussbaum & Senn (eds.) 1993) and "reflexive modernization" (Ulrich Beck, 1994). Uncertainty as a principle leads to the "imperative of responsibility" (Hans Jonas, 1984).