There has been great discussion of the phrase “under God” as it is used in the Pledge of Allegiance over at LanguageLog. The long and the short of it is that the phrase, as used by Lincoln in the Gettysburg Address, from which the words were taken when the Pledge was updated, was not used in the same way as it is in the Pledge. Geoff Nunberg explains:
In short, the phrase “under God” had nothing to do with God’s temporal sovereignity; it was, rather, a way of acknowledging that the efforts of men are always contingent on His providence. And that is how Lincoln intended it, as meaning something like “with God’s help, of course”:
… Lincoln would have had trouble making sense of the use of the words in the Pledge — to him it would have been an ungrammatical way of saying something like, “one nation, with God’s help (of course), indivisible…” or “one nation, after God, indivisible…” As I said in my earlier post, a strategic misreading of history.
Mark Liberman compares this (Lincoln’s) usage to the Arabic phrase “inshallah” meaning “God willing.”