Limits of knowing or the consequences of difficult-access problems for multi-method research and public policy

How can scientists acquire an adequate level of knowledge on phenomena whose actors actively conceal their activities? Social phenomena such as terrorism, sects, corruption, Mafia organizations, drug dealers, or government intelligence agencies actively guard their secrecy, conceal their activities, decide who is allowed (not) to know, and have no interest in being observed or understood by others. The article discusses the consequences of researching difficult-access problems for doing multi-method research. In an ideal-typical approach, we distinguish between social problems that can be easily accessed and those that are difficult to access or non-accessible. To distinguish the two, we define characteristics that eventually lead to the conclusion that scientific inquiry that follows the conventional paradigm of professionalism, transparency, and replicable research reaches its limits when confronted with the active resistance of phenomena that do not like to be observed, understood, or critically approached. From this flows, the necessity to think about interdisciplinary, collaborative, and investigative modes of research that come with various prices.