This is a historical work, but the Introduction is philosophical in spirit. Instead of providing a timetable of the major debates covered in the book, I discuss the principle of “debate” itself as a feature of historical inquiry. I suggest that the primary role of the historian is to explain the conditions which have made rival conceptions of academic freedom plausible. I also discuss some of the leading scholars who have written about academic freedom. Some act as sitting judges on past controversies and do not inform us properly about any arguments with which they disagree. But when one takes pains to portray debates over academic freedom with precision, one is likely to change one’s ideas in the process of writing. The book offers no prescriptions other than the imperative to be well informed about past controversies before taking any position on what academic freedom ought to mean.