Academic freedom is a complex idea, rooted in the 19th century German notion of freedom of teaching and freedom of research. It includes both individual and collective components, in that it can be invoked by an individual professor pursuing knowledge, but also by collective entities such as universities that seek to insulate themselves from state interference. If one includes various textual formulations, academic freedom is
protected in more than half of constitutions in force today. In the United States,
constitutional protection is relatively limited, but the idea has been enshrined in university policies, employment contracts, and documents of the
American Association of University Professors (AAUP).