Tom Van Dyke leaves a thoughtful comment regarding what label best describes key founders -- Washington, Adams, Jefferson, Madison, Franklin, et al. -- "Christian-Deism," or "Theistic Rationalism," or, others may add, perhaps something else (theological, small u unitarianism, as compared to the "Unitarianism" of the 19th Century Congregational Churches). I think all three labels, arguably could suffice for this system that is neither strict deism, nor orthodox Christianity, but somewhere in between with rationalism as the trumping element.
On "Christian-Deism" in particular, I have noted before that broadly defined the key Founders' creed can qualify as both "Christianity" and "Deism." Indeed, the biggest critique I have of Paul Boller's book on Washington's faith is that he defines Christianity narrowly, Deism broadly, and hence proceeds to place Washington in the "Deist," box. Likewise Michael and Jana Novak define Deism narrowly, Christianity broadly, and proceed to place Washington in the "Christian" box. Peter A. Lillback likewise defines Deism narrowly but attempts to prove Washington was an orthodox Trinitarian Christian, but fails to do so. David L. Holmes' terming Washington a "Christian-Deist" is at least fairer than than defining one box broadly, the other narrowly and proceeding to place the founder in whichever box conveniently fits the scholar's secular leftist or religious rightist bias.
The problem with defining "Christianity" or "Deism" broadly is such runs the risk of such a broad understanding that the terms lose their meanings. Indeed, Van Dyke notes that I once noted Jefferson once defined Deism as "the belief of one only God" when referring to the "Deism" of the Jews. That's not a very meaningful definition of Deism. As such Christianity, Judaism, Islam, all qualify as "Deist" religions. What Jefferson defined as Deism in his letter to Benjamin Rush we would better understand as generic theism.
Van Dyke also noted that Jefferson called himself a "Christian." And again, Jefferson could be termed such if we define Christianity broadly. However, Jefferson -- "the Christian" -- rejected the following doctrines:
The immaculate conception of Jesus, his deification, the creation of the world by him, his miraculous powers, his resurrection and visible ascension, his corporeal presence in the Eucharist, the Trinity; original sin, atonement, regeneration, election, orders of Hierarchy, &c.
In defining Christianity so broadly, where do we draw the line? Jefferson rejected just about every doctrine of orthodox Christianity. If that doesn't separate him from the label "Christian," what does? Indeed, in their writings, Jefferson and Adams likewise seemed to define "Christianity" as "generic theism" as well. As Adams put it to Jefferson Oct. 4, 1813, finding "Christianity" in Zeus worship and all of the world's pagan religions:
θέμίς was the Goddess of honesty, Justice, Decency, and right; the Wife of Jove, another name for Juno. She presided over all oracles, deliberations and Counsells. She commanded all Mortals to pray to Jupiter, for all lawful Benefits and Blessings.
Now, is not this, (so far forth) the Essence of Christian devotion? Is not this Christian Piety? Is it not an Acknonowledgement [sic] of the existence of a Supream Being? of his universal Providence? of a righteous Administration of the Government of the Universe? And what can Jews, Christians, or Mahometans do more?
Moses says, Genesis. I. 27. ["]God created man in his own image.” What then is the difference between Cleanthes and Moses? Are not the Being and Attributes of the Supream Being: The Resemblance, the Image the Shadow of God in the Intelligence, and the moral qualities of Man, and the Lawfulness and duty of Prayer, as clear[l]y asserted by Cleanthes as by Moses? And did not the Chaldeans, the Egyptians the Persians the Indians, the Chinese, believe all this, as well as the Jews and Greeks?…I believe Cleanthes to be as good a Christian as Priestley.
Certainly concepts like Deism, Unitarianism, and Universalism derived from the "Christian" tradition. Broadly speaking, therefore, "Christianity" could include these concepts. But then we are left with Christianity, Deism, Unitarianism, Universalism, etc. etc. all meaning the same thing -- "generic theism." And, ironically, that's exactly how Jefferson, Adams, and the other key founders (the "theistic rationalists") would define things.
For instance, in one of Adams' most notable quotations the "Christian Nation" crowd misuses, he writes to Thomas Jefferson on June 28,1813:
“The general principles on which the fathers achieved independence were…the general principles of Christianity…I will avow that I then believed, and now believe, that those general principles of Christianity are as eternal and immutable as the existence and attributes of God; and that those principles of liberty are as unalterable as human nature.”
Adams then more specifically defines those "general principles of Christianity":
Who composed that Army of fine young Fellows that was then before my Eyes? There were among them, Roman Catholicks, English Episcopalians, Scotch and American Presbyterians, Methodists, Moravians, Anababtists, German Lutherans, German Calvinists Universalists, Arians, Priestleyans, Socinians, Independents, Congregationalists, Horse Protestants and House Protestants, Deists and Atheists; and "Protestans qui ne croyent rien ["Protestants who believe nothing"]." Very few however of several of these Species. Nevertheless all Educated in the general Principles of Christianity: and the general Principles of English and American Liberty.
This is not a statement of orthodox Trinitarian Christianity, but of theistic rationalism. As Dr. Frazer put it:
This was clearly not the Christianity of the orthodox, who did not believe that deists, atheists, and those who believe nothing were united with true Christians on any principles of Christianity!