The Manufacturing of Randomness. Art or Science?

The Monte Carlo method is a powerfull instrument to analyze complex systems. It has become a standard tool in almost all fields of science ranging from high energy physics to sociology. Its overall success conceals that the whole method is based on shaky grounds: our ability to generate random numbers. In this talk I will review one of the most spectacular failures of the Monte Carlo method in statistical mechanics, the "Ferrenberg affair" from 1992, and how it has been resolved only recently. This and other disasters teach us that the manufacturing of randomness needs to be promoted from black art to transparent science.