The setting used for "Revelation" is in the early 1960's, somewhere down south in America. The story carries on in the waiting room of the hospital. O'Connor has used third-person omniscient in this story to dramatically contrast the thoughts and words spoken by Ruby Turpin. We can vividly experience being a hypocrite, which is so common through our heads, as any normal human would be, but yet denied to be, through her character. .
Flannery O'Connor's use of the underlying theme, spirituality-versus-evil, is represented very well in this story. There are two ways to view this underlying theme, spirituality-versus-evil. First is the conflict between Mary Grace and Mrs. Turpin. Much to our surprise, and a total opposite to Mrs. Turpin's concept of revelation, an ugly, nasty young woman, Mary Grace, is the mechanism through which the truth is revealed to Mrs. Turpin. The strange young woman is, in fact, reminiscent of an Old Testament prophet with her piercing eyes and her rude, uncompromising message. In the end, when Mrs. Turpin scolds God and demands that he justify himself to her, he answers with a vision in which, literally, the last (in Mrs. Turpin's scheme of reality) become first. This powerful scene also has biblical overtones: the scene in which Job, the righteous man who never did anything wrong, demands that Yahweh explain why he has allowed Job to suffer, and Yahweh speaks. It shows the underlying patterns first used by the Bible, and then reused here by O'Connor.
Another way to view the underlying theme, spirituality-versus-evil, is the conflict Mrs. Turpin has within herself. Her outer-self strongly believes that she's a good, moral, and blessed person. This clearly shows when she categorize herself as superior to most everyone in the hospital room, and categorize others as white trash, ugly, fat girl, and so on. But we have to look closely not to misunderstand that Mrs. Turpin is confident with her life.