Mathematics turned inside out: the intensive faculty versus the extensive faculty

Research universities in the United States have larger mathematics faculties outside their mathematics departments than inside. Members of this “extensive” faculty conduct most mathematics research, their interests are the most heavily published areas of mathematics, and they teach this mathematics in upper division courses independent of mathematics departments. The existence of this de facto faculty challenges the pertinence of institutional and national policies for higher education in mathematics, and of philosophical and sociological studies of mathematics that are limited to mathematics departments alone.