In 1968 the sociologist Niklas Luhmann was appointed to a chair of sociology at the new University of Bielefeld. At the end of the 1960s he was asked there to name his research project. He wrote: “Theorie der Gesellschaft; Laufzeit: 30 Jahre; Kosten: keine.” Theory of society. Duration: 30 years. Cost: none. His main tool was a Zettelkasten, a card index he had kept since the 1950s. It grew to about 90,000 notes. His Die Gesellschaft der Gesellschaft, The Society of Society, appeared in 1997, shortly before his death.