Who serves as a moral compass for the occupants of the bardo in the book, Lincoln in the Bardo: A Novel?

Reverend Thomas acts as a moral compass for the group and has a tendency to preach to his fellow occupants of the bardo. Unlike Vollman and Bevins, Thomas does suspect that they are all dead. On this suspicion, Thomas goes off to explore the bardo on his own, face the truths of his life, and ultimately pass on to the next life.