Some think open Deism was the driver behind the revolution and the Constitution; it wasn't. Others think almost all of the Founders were orthodox Christians, and the exceptions like Jefferson were open about their Deism; that's not right either. During America's Founding, disbelief in the Trinity could get one in social, perhaps legal trouble with the institutional forces of orthodox Trinitarian Christianity. And being an open Deist and mocker of Christianity could ruin one's public reputation: See Thomas Paine.
Even Jefferson was not open about what he believed (or disbelieved) in the Christian system. Rather heretics and infidels who wanted to remain in positions of social power tended to nominally belong to orthodox churches, and, for good reason, keep silent about their infidelity. But sometimes the more philosophically minded ones wrote in code in their public arguments. There is a certain kernel of truth in the Straussian notion of esoteric messages. In Jefferson's case, the charges of Deism leveled against him by the orthodox clergy stemmed almost entirely from his sentiments in his public book "Notes on the State of Virginia" (heretofore referred to as "Notes"). The offending passage follows:
But it does me no injury for my neighbor to say there are twenty gods or no God. It neither picks my pocket nor breaks my leg.
Orthodox minister John Mason termed this "the morality of devils." The offending passage, in the minds of Mason and others, conclusively demonstrated that Jefferson was an infidel/Deist. However, Jefferson never said in "Notes," "here is what I believe, I am a Deist, I reject the Trinity, etc." All of the smoking gun quotations of Jefferson denying the tenets of orthodox Christianity come from his private letters. Mason and others essentially tried to glean a Straussian, esoteric message from the text. And because Jefferson, in "Notes," never denied Christianity or claimed to be a Deist, a few Christian ministers could come to his defense, for instance Tunis Wortman who wrote the following, responding to Mason:
I have seen nothing to convince me that Mr. Jefferson is a deist. On the contrary from information, at least, as respectable as that of the author of the pitiful pamphlet, which I shall presently condescend to notice, my information is that he is a sincere professor of christianity—though not a noisy one. But, I will candidly confess to you, that if I had ever so sincere a conviction of his infidelity; my prejudices, if you will permit me to call them so, are not so strong as to sacrifice my country to their operation; believing as I do, that public liberty and the constitution, will not be safe under the administration of Mr. Adams or Mr. Pinckney; I cannot see that the christianity of either of them will atone for the loss of my political freedom. There may be some merit in sacrificing every thing to the sign or external symbol of the cross; but it is a merit to which I do not aspire. If the other candidates were republicans, and Mr. Jefferson a deist, then the religion of the former would turn the scale of opinion in their favor; but, I never will be duped by the christianity of any man that meditates the ruin of the constitution. I am not prepared to surrender my liberty civil and religious, the future happiness of my children, the prosperity of my country, the welfare of millions of human beings yet unborn, and every possession and enjoyment that is valuable to men, and patriots, and christians. I know, that my God requires not such a sacrifice; he that would not permit Abraham to give his son Isaac as a burnt offering, demands not that my country should be prostrated on the altars of his religion; the infernal rites of Moloch required human victims, and a priest of Moloch would delight in the sacrifice of hecatombs. But christianity is the religion of grace, & mercy, and justice, and liberty.
In the first place, Mr. Jefferson is supposed to deny the existence of an universal flood, such as Moses describes, and jews and christians equally believe. This is not the fact.
I do aver, that there is not a sentence in the notes upon Virginia, which either expressly, or even by implication denies the existence of such flood. By a recurrence to that work, we will readily perceive that the deluge is a topic collateral to the principal subject of discussion. In answer to questions either actually made, or supposed to have been asked by a learned foreigner, Mr. Jefferson is proceeding to describe the principal productions of his native state; while employed in this task; a remarkable and an interesting phenomenon arrests his attention, that is, the existence of petrified shells, or calcareous substances on the tops, or near the surfaces of the highest mountains. That circumstance “is considered by many both of the learned and the unlearned as proof of an universal deluge.” Mr. Jefferson, on the contrary, is inclined to believe that such fact alone, unsupported by higher authority, would not amount to proof of a deluge.
Only in looking back at Jefferson's life and letters do we know what he really believed: He was not, as the orthodox concluded, an atheist or a strict Deist. He thought himself a unitarian, thought true Christianity was unitarian, not trinitarian, and essentially rejected all of the doctrines of orthodox Christianity, while still believing in a benevolent, active personal God. For all of the drama over Jefferson's religiosity or lack thereof during the Jefferson/Adams election, a great irony is that Jefferson's and Adams' later resumed correspondence shows they were of one mind on God's attributes.
Adams likewise did not publicly proclaim his theological unitarianism; or he too would have been scolded by the orthodox (who supported him against in the election of 1800 against Jefferson). Although somewhat later in life, when Unitarianism was more socially acceptable, he did "come out of the closet," in this regard (see his letter to J. Morse below; earlier on, these Founders would entrust their friends only, often likeminded heretics, with their religious secrets; this certainly was not the case when Adams proudly proclaimed his unitarianism to Morse).
This is one reason why when investigating the religious beliefs of America's Founders, when one sees in their public addresses both systematic refusal to discuss religious specifies, and systematic use of generic philosophical terms for God -- what we see with Washington, Madison, Hamilton, G. Morris, and many others -- this strongly suggests, in my opinion, secret religious heterodoxy.
While they may have kept religious secrets, America's Founders were not silent about founding the nation on enlightenment, reason, and natural rights, notably rights of conscience. Those ideas were openly promoted. Some of these ideas were pregnant with implications, indeed, as the orthodox rightly feared, subversive implications, that would bear themselves out years later. For instance, the notion that men have an unalienable right to worship no God or twenty God means God grants men a right to worship false gods or break the first tablet of the Ten Commandments. Jefferson hoped by Founding America on man's enlightened reason, the Christian religion would rationally reform so that everyone would become unitarians like he and Adams. As he noted in 1822, “there is not a young man now living in the US who will not die an Unitarian,...”
As secret heretics and infidels, the key Founders would personally gain if the rights of conscience and free speech permitted men to openly profess heresy and infidelity. And indeed, this is exactly what happened. A few hundred years earlier, in Calvin's Geneva, Servetus was put to death for publicly denying the Trinity. Joseph Priestley -- popular among elite Whigs, but not at all among the masses -- established one of the first Unitarian Churches in 1796. Harvard bred secret unitarians in the mid 18th Century. John Adams testified that his own Church had preached unitarianism as of 1750. Harvard officially became Unitarian in 1805 when they elected Henry Ware, Hollis Professor of Divinity. Because Unitarianism had "come out of the closet," so to speak, there was some confusion as to its age. Orthodox figure Jedidiah Morse wrote a pamphlet in 1815 attacking the Unitarian heresy and claimed it was only 30 years old. He sent the pamphlet to proud unitarian John Adams who replied with somewhat of an acerbic tone:
I thank you for your favour of the 10th and the pamphlet enclosed, “American Unitarianism.” I have turned over its leaves and have found nothing that was not familiarly known to me.
In the preface Unitarianism is represented as only thirty years old in New England. I can testify as a Witness to its old age. Sixty five years ago my own minister the Reverend Samuel Bryant, Dr. Johnathan Mayhew of the west Church in Boston, the Reverend Mr. Shute of Hingham, the Reverend John Brown of Cohasset & perhaps equal to all if not above all the Reverend Mr. Gay of Hingham were Unitarians. Among the Laity how many could I name, Lawyers, Physicians, Tradesman, farmers!
-- John Adams to Jedidiah Morse, May 15, 1815. Adams Papers (microfilm), reel 122, Library of Congress.
As Adams noted the rights of conscience also were inconsistent with blasphemy laws. Keep in mind, most originalists believe that the public meaning of the words, not secret private intent of the Framers is dispositive. However, as noted above, the principles contained in those words are pregnant with implications. When one examines the private intent and one sees key Founders repeatedly discussing what they hoped to achieve by publicly founding America on particular principles and then this is exactly what happens, such is telling to say the least.