Academic freedom is commonly perceived as the right of college and university professors to teach and to engage in research and publication without undue restrictions placed on these activities. The modern concept of academic freedom derives from the principles of Lehrfreiheit and Lernfreiheit, which were formulated and practiced by the University of Berlin in the early nineteenth century. In the United States, academic freedom is associated with the First Amendment's protection of freedom of expression. The principle of academic freedom grew and developed during the Enlightenment. Academic-freedom cases involved protecting faculty and educational institutions from external pressures, such as might be involved in overly intrusive governmental investigations. The ubiquitous presence and utility of the Internet as a means of communication and learning, including distance education, e-mail as a form of communication, and the creation of faculty and student Web pages, pose several threats to academic freedom.