Who are the Ulms in the novel, To Rise Again at a Decent Hour?

The Ulms are a religious group of people who believe God commanded them to doubt his existence. They have been on the verge of extinction for thousands of years and have been so secret that most people have never heard of them. They seek out “reclaimants” who are descended from members of the tribe but are no longer living among the Ulms. Paul is one of those.