I'm going to do a little bit more nitpicking on Michael and Jana Novak's conception of Washington's God. Check out their latest post on July 4 and God.
The Novaks, in their book, have noted that Washington's God is "Judeo-Christian" and not "Deist." "Deist" may not be the proper term for Washington's (or Franklin's or Jefferson's) God. But "Judeo-Christian" is clearly too restrictive.
Just because Judaism and Christianity, like Washington and the other key Founders, posit the notion of a warm intervening God that takes an interest in man's affairs, doesn't therefore mean the Founders' God is the God of the Bible, or as Novak likes to put it, the God who gave the Ten Commandments to Moses. In fact, our rationalistic Founders, of which Washington was one, doubted much of Revelation, specifically they doubted that God revealed the Ten Commandments to Moses.
The Novaks, like pretty much all scholars, have a theory which they are trying to peddle, and view the facts to support that theory. In particular, to support the notion that Washington's God was the God of the Bible, they stress one letter Washington wrote to the Hebrew Congregation in Savannah, in particular this passage:
May the same wonder-working Deity, who long since delivered the Hebrews from their Egyptian oppressors, planted them in a promised land, whose providential agency has lately been conspicuous in establishing these United States as an independent nation, still continue to water them with the dews of heaven and make the inhabitants of every denomination participate in the temporal and spiritual blessings of that people whose God is Jehovah.
Because of that passage, the Novaks claim that Washington's God "is Jehovah" or "the Judeo-Christian" God. Well, I have a theory too. George Washington, like the other key Founders, was a religious universalist who believed that all (more or less) religions were valid ways to God. To the extent that Christianity makes exclusive claims about God is the extent that our key Founders' religion conflicts with orthodox Christianity.
As a universalist, Washington would "speak in the terms" of the particular religion he was addressing. Washington (as far as I know) only ever referred to God as Jehovah when addressing the Jews. Likewise, when Washington addressed his fellow Freemasons, he referred to God on their terms as "the Great Architect of the Universe." And, when Washington addressed the Cherokee Nation, Washington referred to God as "the Great Spirit," which is how they referred to God.
Paul Boller notes that Washington specifically crossed out the word "God" from one of his speeches (perhaps Boller was referencing the Cherokee speech, I'm not sure) to the Indians and specifically wrote in "the Great Spirit." George Washington and Religion, p 69 (note I don't have Boller's book but am referencing Gregg Frazer's Ph.D. thesis).
Using the Novak's method of categorization, when asked "who is Washington's God?" we could likewise say "the Great Architect of the Universe" the Freemasons worshipped, or even "the Great Spirit" the Cherokees worshipped.