During recent years scientists coming from the ecologist and molecular biologist traditions have argued very differently about the risks of deliberate release of genetically engineered micro-organisms (GEOs) into the environment. When actual guidelines for regulation have been drawn up and “scientific experts” have been consulted, representatives of these different scientific camps have given quite different advice. In fact, we have a tacit battle between scientific experts as to who has the right to speak “for” science to the public and policy makers. It seems that the molecular biologists so far have had the upper hand because of concrete and spectacular achievements in this field. Meanwhile, these experts can profit from the fact that the general public and policy makers tend to see science as a unified enterprise and are typically unaware of systematic differences in conceptions about science between experts from different scientific traditions. Thus, a scientist from any scientific field may easily be seen as an expert on science in general.