When a person stops using the body, everything about his or her thoughts, attitudes, personality, and beliefs remains the same. For some, when they leave the body, they retain their religious beliefs for years or decades. The speakers in Leslie Flint seances describe materialist scientists who have died who are still trying to discover how the after they're in is a materialistic phenomenon.
They also describe people who cling to the religious beliefs they held while on the Earthly plane. They have not evolved spiritually to leave the beliefs behind, although Flint's guide, Dr. Marshal, calls these people "not very evolved" and assures us that they will eventually grow beyond the religious beliefs. Some are is groups waiting for the rapture and second coming of Christ when they will be caught up to heaven.