Passage 4 Questions 16 to 20 are based on the following passage. When the American Association of University Professors （AAUP） was organized in 1915, its founders proclaimed an ideal of academic freedom as essential to the definition of a university. At first some academic administrators resisted aspects of the due process in hiring and firing that the AAUP insisted; but within the next two decades academic freedom, more or less as the AAUP had defined it, was widely accepted. By 1940 when an important restatement of the AAUP principles was widely adopted, the ideal had become a standard assumption in American academic thought. Certainly by the end of the era of the early 1950s academic freedom had attained sacred status among professors and was spoken of as though it were an ancient absolute associated with universities since the ancient time. The direct inspiration for the modem American conception of academic freedom came, however, from Germany, or at least from the romanticized （理想化的）impressions of Germany that the many thousands of American academics who studied there brought back with them. Particularly important for the American organizers of the academic profession after 1890 was the German Lehrfreiheit （教学自由），referring to freedom for university professors. In Germany this freedom included, first, the rights for professors to teach whatever they chose with a minimum of administrative regulations and, second, the freedom to conduct one5s research and to report one5s findings in lectures and publications without external restraint. The Americans typically understood Lehrfreiheit as the modem ideal that truth is progressive and that for science to advance it must be freed from tradition and assumption. In 19th century Germany this outlook was associated with the term Wissenschaft （科学）, which meant more than just title English word “science，” suggesting an ideal scientific research for truth. German Protestant universities only gradually won full approval of such autonomy, including freedom from occasional Christian church interference. Nonetheless, they were always far in advance of American schools and by the time of the establishment of the German Empire Lehrfreiheit had become a legal practice protected by law. It controlled the universities and protected them from direct interference of other interests. In a society far more conscious of status than the United States，Lehrfreiheit did not suggest any general commitment to freedom for all citizens. Once the wider applications of modern Lehrfreiheit were accepted, they were proclaimed as essential to any institution calling itself a “university.”What can we learn about the idea of Lehrfreiheit from the passage?