An interesting thesis for O'Connor's "Parker's Back" is that the writer dramatizes in the story the heresy (for Catholics) "which denies Our Lord corporeal substance," in the words of Caroline Gordon, O'Connor's proofreader and life-long friend. O. E. Parker, one of the most grotesque characters that populate her fiction, obsessively inscribes his body with tattoos of various shapes, from anchors and tigers to the British Queen Elizabeth II and her husband Philip, along with "a few obscenities" on his abdomen, "but only because that seemed the proper place for it." The only empty space on his skin is the back; the rest is densely inscribed with an intricate text that tells of Parker's life as a sailor, and in an allegorical sense, as a sinner. It is quite clear that O'Connor is using two of her favorite literary modes, the grotesque and the allegorical, to illustrate her belief in the corporeality of God and therefore in the power that representations of the Lord have to tell us of His true existence. And yet, the story remains in an ambiguous terrain that is open to multiple interpretations.
Parker's given names are Obadiah (God's servant in Hebrew) Elihue (my God is him), and both names turn him into a biblical personage, a modern-day prophet, albeit a grotesque one, who receives a number of irresistible signs (the most important one while he is bailing hay and hears a loud voice that says 'GOD ABOVE') until he realizes the purpose of the empty space on his back. And once he has the image of a Byzantine Christ inscribed on his textual skin, Parker literally goes back to his friends and his wife, now a changed man. And while his friends make fun of the newest tattoo and his wife Sarah accuses him of idolatry, we readers understand that Parker has reached redemption (in a literal sense from his past dependance on others and, in a spiritual one, forgiveness his sinful soul) and has become a living testimony of the tangible existence of God.
I hope these ideas may help guide your paper.