Should a pope resign his office?

In his book-length interview with Peter Seewald, Light of the World, Pope Benedict responded to Seewald's question as to whether a pope should resign saying, "Yes. If a Pope clearly realizes that he is no longer physically, psychologically, and spiritually capable of handling the duties of his office, then he has a right and, under some circumstances, also an obligation to resign."

And, now Benedict has done it.