The world of nanotechnology is full of folk theories. Actors attempt to capture patterns in what is happening and be reflexive about them, so as to do better the next time. A clear example is the diagnosis of an impasse in agro-food GM technologies, coupled to statements about the need to avoid such impasses with nanotechnology. Since there is a claim that such patterns will recur (if we don't change our ways), there is generalization, so one can speak of a theory—here about public reactions to new technology. Calling it a folk theory implies that it evolves in ongoing practices, and serves the purposes of the members of the various practices. In this example, these would be nanotechnologists, policy makers for nanotechnology, other scientists and technologists, science watchers and commentators. What characterizes folk theories is that they provide orientation for future action.