Universities can and have existed without academic freedom and academic tenure. But academic freedom is necessary for a university dedicated to the pursuit of knowledge in a democratic society. Both academic freedom and academic tenure are not only rights but also carry with them moral obligations. Furthermore academic tenure is the best defense of academic freedom that American universities have found. Academic tenure can be successfully defended from the many contemporary attacks to which it is being subjected only insofar as it is necessary to defend academic freedom, and only if all involved in the system of tenure observe the ethical requirements that the system demands.