The network paradigm dominated immunological research from the early 1970s to the late 1980s. The originator, Niels Jerne, hypothesized that the vast diversity of antibodies in each individual forms a network of mutual "idiotypic" recognition, thus regulating the immune system. In context of emerging concepts of systems biology such as cybernetics and autopoesis, the "Eigenbehavior" of the immune system fascinated an entire generation of young immunologists. But fascination led to experimental errors and overinterpretation, eventually magnifying the immune system from a mere infection-fighting device to a substrate of personality and individuality. As a result, what initially appeared as an exciting new perspective of the immune system is now viewed as a scientific vagary, and is largely abandoned.The author, himself a participant in the network vagary, begins with a description of the leading theoretical concepts on fact finding in science. This is followed by a historical account of the rise and fall of the network paradigm, complemented by personal interviews with some of the prominent protagonists. By comparing the network paradigm to other, more lasting concepts in life science, the author develops a general perspective on how solid knowledge is derived from error-prone scientific methodology, namely by exposure of scientific notions to the scrutiny of reality.