English Faculty Library), and by colleges (each of which maintains a multi-discipline library for the use of its members). Central governance The university's formal head is the Chancellor, currently Lord Patten of Barnes, though as at most British universities, the Chancellor is a titular figure and is not involved with the day-to-day running of the university. The Chancellor is elected by the members of Convocation, a body comprising all graduates of the university, and holds office until death. The Vice-Chancellor, currently Irene Tracey, is the de facto head of the university. Five pro-vice-chancellors have specific responsibilities for education; research; planning and resources; development and external affairs; and personnel and equal opportunities. The University Council is the executive policy-forming body, which consists of the vice-chancellor as well as heads of departments and other members elected by Congregation, in addition to observers from the students' union. Congregation, the "parliament of the dons", comprises over 3,700 members of the university's academic and administrative staff, and has ultimate responsibility for legislative matters: it discusses and pronounces on policies proposed by the University Council. Two university proctors, elected annually on a rotating basis from two of the colleges, are the internal ombudsmen who make sure that the university and its members adhere to its statutes. This role incorporates student discipline and complaints, as well as oversight of the university's proceedings. The university's professors are collectively referred to as the Statutory Professors of the University of Oxford. They are particularly influential in the running of the university's graduate programmes. Examples of statutory professors are the Chichele Professorships and the Drummond Professor of Political Economy. The various academic faculties, departments, and institutes are organised into four divisions, each with its own head and elected board. They are the Humanities Division; the Social Sciences Division; the Mathematical, Physical and Life Sciences Division; and the Medical Sciences Division. The University of Oxford is a "public university" in the sense that it receives some public money from the government, but it is a "private university" in the sense that it is entirely self-governing and, in theory, could choose to become entirely private by rejecting public funds. Colleges To be a member of the university, all students, and most academic staff, must also be a member of a college or hall. There are thirty-nine colleges of the University of Oxford and five permanent private halls (PPHs), each controlling its membership and