“I’ll tell you God’s truth.”
Gatsby is trying so hard to convince Nick that he truly is old money that he has no problem bringing up God’s name just to prove a point. We have plenty of evidence to believe he might be lying, but Gatsby is insistent that this is the honest truth.
God seems to have very little value, or at least, a very much corrupted value, throughout the novel. Just as T.J Eckleburg is viewed as the eyes of God in this world, and thus mixes consumerism with religion, Gatsby isn’t bothered about claiming a lie is “God’s truth”.
To help improve the meaning of these lyrics, visit “The Great Gatsby (Chapter IV)” by F. Scott Fitzgerald and leave a comment on the lyrics box