My co-blogger at American Creation, King of Ireland, aka Joe Winpisinger, like many of America's Founders (Jefferson, J. Adams, Franklin, etc.) identifies himself as a "rational Christian," and defends the political theology of the American Founding as "rational Christianity."
Check out his excellent post articulating where he is coming from. (Note, I helped him edit the post).
I argue the history of Christianity, properly understood, provided the fertile ground that launched modernity and as such those who invoke the authority of "science" and "rationality" should be less hostile, as many of them oft-seem, to what I term "rational Christianity," a theological system that helped bring about science, rationality and political liberty. Thomas Aquinas, Isaac Newton and many American Founders stand as the best representatives of the "rational Christian" tradition that I defend.
I see America's Declaration of Independence -- a document that posits the universal natural ends of government -- as typifying "rational Christianity." Indeed it was written by "rational Christians" Thomas Jefferson, John Adams and Ben Franklin and supported by "rational Christians" like Sam Adams. But wait, didn't John Adams -- a unitarian -- practice a different religion than that of his cousin Samuel, a Calvinistic Trinitarian? The kind of rational Christianity for which I argue transcends such sectarian differences. Issues of salvation/heresy such as whether Jesus is the second person in the Trinity matter not to the political-theological tradition of "rational Christianity" that I (after America's Founders) endorse.
The "rational Christian" political theology of the DOI, while having nothing to do with orthodox doctrines like the Trinity, rather relates to strongly established philosophical traditions in Christianity like Imago Dei, Aquinas' incorporation of Aristotle into Christendom (Jefferson sourced Aristotle as one of the four prime ideological sources behind the DOI), and the doctrine of "interposition" developed by the Calvinists.
Many Christian factions and sects had to work with one another and compromise under one big tent in order to successfully declare independence from Great Britain. Their sectarian differences were irreconcilable; those divided them. But "rational traditions" within Christianity united them.
One of the largest factions among them who proved themselves willing to follow the demands of "rational Christianity" was, believe it or not, the Calvinists. While many Calvinists certainly remained loyalists (Calvin's himself provided much dicta that would seem to support the loyalist position), those Calvinists sympathetic to a pro-resistance Whig position had a long established intellectual tradition of "Interposition" from which to draw and the "rational Christians" further supported such position with what man's reason discovered in Nature.
The American Founding, at its heart, invoked a Christian ecumenicism. They embraced John Locke -- a man whose Christology remains a mystery and whom the orthodox Trintiarians and heterodox unitarians both followed -- and his teachings on, among other things, religious toleration and political liberty.
The Declaration of Independence, as a document of political theology articulated a Lockean "rational Christianity" around which Calvinists, Arminians, unitarians and deistically minded Christians could rally.