“Revelation,” like much of Flannery O’Connor’s fiction, deals with the central Christian sin of pride. “Pride” in this sense means selfishness, self-centeredness, and a failure to recognize and worship the primacy of God.
Mrs. Turpin, like many of O’Connor’s characters, needs to be humbled. She deeds to develop more fully her true potential as a creature of God. She needs to be brought low in order that she may rise in a truer sense.
She begins her journey toward a full revelation of her relationship with God when she is literally brought low by the appropriately named (if highly grotesque) character named Mary Grace, who quite literally “throws the book” at her – a book significantly titled Human Development.
The “life-giving knowledge” that Mrs. Turpin begins to achieve by the end of the story is that pride of any sort must be burned away if anyone can hope to achieve a right relationship with God. Spiritual pride – the presumption that one’s relationship with God is already right – especially needs to the burned away.