Society of Senior Scholars
The Society of Senior Scholars "are a select group of scholar-teachers who wish to continue part-time teaching in the general education programs of Columbia University after their retirement from full-time service." In short, it's an organization of legendary emeriti professors who want to keep teaching sections of the Core Curriculum. The program, initiated by Prof. Wm. Theodore de Bary in 1988, is currently operated under the auspices of the Heyman Center. Its executive director is James Mirollo.
Faculty members are elected to the society upon retirement. It allows them to continue teaching core sections, and allows the College to maintain the strength of the faculty teaching the core. A cynical view is that it keeps older faculty teaching the Core to cover for the disinterest on the part of younger faculty in teaching sections.