Before the financial crisis, the political and economic experts pretended to know everything; in the financial crisis, they suddenly know nothing any more (without really admitting this to themselves and to the public). The crisis of the globalised financial markets has again brought home in a dramatic way to a both amazed and deeply distraught public that, especially in the self-proclaimed knowledge societies, phenomena and dynamics of non-knowing are acquiring an importance that is difficult to overestimate as the scale of the threat emanating from civilisation increases. Who – apart from a handful of Cassandras who were mostly dismissed as mavericks and ‘prophets of doom’ – foresaw, or even had an inkling, that within a short space of time the financial sector would experience dramatic collapses across the globe (Beck 2009), that major banks could be prevented from going under only through state aid on a gigantic scale and that even whole states could be rescued from bankruptcy only with difficulty? In retrospect it turned out that the actors who made such a show of their knowledge in the financial markets did not know what they had got themselves into with the so-called innovative financial products. At any rate, they were incapable of assessing the associated risks. The financial crisis is not the only example which illustrates the explosive power of what is not known in contemporary societies. The threatening, man-made climate change, too, and the potential, but unknown consequences of the release of genetically modified organisms (GMOs), of the spread of ‘swine flu’ viruses and of the diffusion of environmental chemicals throughout the world emphatically underline that, notwithstanding all assertions to the contrary, numerous spheres of action and politics in contemporary societies are conditioned by non-knowing rather than by knowledge. 1 Especially in a world of delimited threats – world risk society – we are compelled to act under conditions of more or less non-knowing: that is the message which has the significance of a ticking political time bomb.