With a series of four sieves, the University pans for its professors. The number of teachers who remain at the end of this selective process is small, since the University is continually sifting them. The prospective professor begins as a teaching fellow, a graduate student working for his doctorate. One of some 400, he is the primal form of faculty life. Frequently he must have completed most of his Ph.D. work, have passed his exams, and be writing his thesis to be accepted for the post. He is selected by his department, approved by the faculty dean, and given a maximum of four successive yearly appointments. He can expect to receive all four, but is free to leave for a better post elsewhere at any time. While here, however, he may teach no more than three fifths of his time.

When the teaching fellow has run through his last appointment and his graduate work is completed, he has an eight to one chance of staying here. The Faculty of Arts and Sciences carries only 50 men in the next position in the faculty hierarchy, the instructor post. The same authorities pick the men, but the Corporation must approve the choice since this is a full-time job. It amounts to three consecutive one-year appointments, but the instructor again may withdraw if he wishes.

The two succeeding steps are the crucial ones, which most often force the aspiring professor to leave Cambridge. His department and dean must recommend him for the rank of assistant professor, which carries a five-year term and is not renewable. The awarding of this post does not depend solely on the candidate's capabilities; for while the number of teaching fellows and instructors may vary from year to year, each department has only a limited number of professorial openings. There are approximately 75 assistant professorships in the College.

In the fourth year of his appointment, the assistant professor again must pass under the scrutiny of his superiors. This time his department must consider whether to drop him or keep him forever. An ad hoe committee is formed to make recommendations on his case. If the applicant is turned down, he still has a year of security in which to seek employment elsewhere. If he is to be retained and elevated, he must obtain the approval of the Corporation and Overseers, for the rise from assistant to associate professor is a change from a temporary to a permanent post. The decision is so important that the Overseers table the application for two weeks in order to study it.

The College lists 60 associate professors and 170 full professors, but the final promotion to the latter rank is not automatic. Many never move up. An associate professor must pass through six salary increases before he can reach the top. The first five are annual increases; the last is not automatic.

Meanwhile, there are additional appointments on the way up. The position of Allston Burr Senior Tutor is usually awarded to an assistant professor, but instructors have held it. It is normally a five-year post but it can be altered to fit the expiration date of a shorter appointment already held. The Senior Tutor devotes half of his time to teaching and half to House administrative matters. The position of Housemaster, awarded by the President and the Corporation, entails the same duties.