The following are excerpts from Thomas Jefferson's Deistic refutations of the Trinity. taken from http://www.sullivan-county.com/deism/jeff_letters.htm
Letters from Thomas Jefferson are as follows:
----- To John Adams, 1813
It is too late in the day for men of sincerity to pretend they believe in the Platonic mysticisms that three are one, and one is three; and yet that the one is not three, and the three are not one . . . But this constitutes the craft, the power and the profit of the priests. Sweep away their gossamer fabrics of factitious religion, and they would catch no more flies. We should all then, like the Quakers, live without an order of priests, moralize for ourselves, follow the oracle of conscience, and say nothing about what no man can understand, nor therefore believe.
----- To Dr. Waterhouse, 1815
The priests have so disfigured the simple religion of Jesus that no one who reads the sophistications they have engrafted on it, from the jargon of Plato, of Aristotle and other mystics, would conceive these could have been fathered on the sublime preacher of the Sermon on the Mount. Yet, knowing the importance of names, they have assumed that of Christians, while they are mere Platonists, or anything rather than disciples of Jesus.
----- To Carey, 1816: N. Y. Pub Lib., MS, IV, 409
On the dogmas of religion, as distinguished from moral principles, all mankind, from the beginning of the world to this day, have been quarreling, fighting, burning and torturing one another, for abstractions unintelligible to themselves and to all others, and absolutely beyond the comprehension of the human mind. Were I to enter on that arena, I should only add an unit to the number of Bedlamites.
----- To Van der Kemp, 1816
Altho' I rarely waste time in reading on theological subjects, as mangled by our Pseudo-Christians, yet I can readily suppose Basanistos may be amusing. Ridicule is the only weapon which can be used against unintelligible propositions. Ideas must be distinct before reason can act upon them; and no man ever had a distinct idea of the trinity. It is mere Abracadabra of the mountebanks calling themselves the priests of Jesus. If it could be understood it would not answer their purpose. Their security is in their faculty of shedding darkness, like the scuttlefish, thro' the element in which they move, and making it impenetrable to the eye of a pursuing enemy, and there they will skulk.
----- To C. Thompson, 1816
I am a real Christian, that is to say, a disciple of the doctrines of Jesus, very different from the Platonists, who call me infidel and themselves Christians and preachers of the gospel, while they draw all their characteristic dogmas from what its author never said nor saw. They have compounded from the heathen mysteries a system beyond the comprehension of man, of which the great reformer of the vicious ethics of deism of the Jews, were he to return on earth, would not recognize one feature.
----- To E. Styles, 1819
I am not [a Calvinist]. I am of a sect by myself, as far as I know. I am not a Jew, and therefore do not adopt their theology, which supposes the God of infinite justice to punish the sins of the fathers upon their children, unto the third and fourth generation; and the benevolent and sublime reformer of that religion has told us only that God is good and perfect, but has not defined him. I am, therefore, of his theology, believing that we have neither words nor ideas adequate to that definition. And if we could all, after this example, leave the subject as undefinable, we should all be of one sect, doers of good, and eschewers of evil. No doctrines of his lead to schism. It is the speculations of crazy theologists which have made a Babel of a religion the most moral and sublime ever preached to man, and calculated to heal, and not to create differences. These religious animosities I impute to those who call themselves his ministers, and who engraft their casuistries on the stock of his simple precepts. I am sometimes more angry with them than is authorized by the blessed charities which he preaches.
----- To Van der Kemp, 1820
The genuine and simple religion of Jesus will one day be restored: such as it was preached and practised by himself. Very soon after his death it became muffled up in mysteries, and has been ever since kept in concealment from the vulgar eye. To penetrate and dissipate these clouds of darkness, the general mind must be strengthened by education.
----- To Dr. Benjamin Waterhouse, June 26, 1822
Dear Sir,- I have received and read with thankfulness and pleasure your denunciation of the abuses of tobacco and wine. Yet, however sound in its principles, I expect it will be but a sermon to the wind. You will find it as difficult to inculcate these sanative precepts on the sensualities of the present day, as to convince an Athanasian that there is but one God. I wish success to both attempts, and am happy to learn from you that the latter, at least, is making progress, and the more rapidly in proportion as our Platonizing Christians make more stir and noise about it. The doctrines of Jesus are simple, and tend all to the happiness of man.
1. That there is one only God, and he all perfect.
2. That there is a future state of rewards and punishments.
3. That to love God with all thy heart and thy neighbor as thyself, is the sum of religion.
These are the great points on which he endeavored to reform the religion of the Jews. But compare with these the demoralizing dogmas of Calvin.
1. That there are three Gods.
2. That good works, or the love of our neighbor, are nothing.
3 That faith is every thing, and the more incomprehensible the proposition, the more merit in its faith.
4. That reason in religion is of unlawful use.
5. That God, from the beginning, elected certain individuals to be saved, and certain others to be damned; and that no crimes of the former can damn them; no virtues of the latter save.
Now, which of these is the true and charitable Christian? He who believes and acts on the simple doctrines of Jesus? Or the impious dogmatists, as Athanasius and Calvin? Verily I say these are the false shepherds foretold as to enter not by the door into the sheepfold, but to climb up some other way. They are mere usurpers of the Christian name, teaching a counter-religion made up of the deliria of crazy imaginations, as foreign from Christianity as is that of Mahomet. Their blasphemies have driven thinking men into infidelity, who have too hastily rejected the supposed author himself, with the horrors so falsely imputed to him. Had the doctrines of Jesus been preached always as pure as they came from his lips, the whole civilized world would now have been Christian. I rejoice that in this blessed country of free inquiry and belief, which has surrendered its creed and conscience to neither kings nor priests, the genuine doctrine of one only God is reviving, and I trust that there is not a young man now living in the United States who will not die an Unitarian.
But much I fear, that when this great truth shall be re-established, its votaries will fall into the fatal error of fabricating formulas of creed and confessions of faith, the engines which so soon destroyed the religion of Jesus, and made of Christendom a mere Aceldama; that they will give up morals for mysteries, and Jesus for Plato. How much wiser are the Quakers, who, agreeing in the fundamental doctrines of the gospel, schismatize about no mysteries, and, keeping within the pale of common sense, suffer no speculative differences of opinion, any more than of feature, to impair the love of their brethren. Be this the wisdom of Unitarians, this the holy mantle which shall cover within its charitable circumference all who believe in one God, and who love their neighbor! I conclude my sermon with sincere assurances of my friendly esteem and respect.
----- An additional letter to theologian James Smith -- December 8, 1822 -- further elaborates Jefferson's views on the subject.
"Sir, -- I have to thank you for your pamphlets on the subject of Unitarianism, and to express my gratification with your efforts for the revival of primitive Christianity in your quarter.
No historical fact is better established, than that the doctrine of one God, pure and uncompounded, was that of the early ages of Christianity; and was among the efficacious doctrines which gave it triumph over the polytheism of the ancients, sickened with the absurdities of their own theology. Nor was the unity of the Supreme Being ousted from the Christian creed by the force of reason, but by the sword of civil government, wielded at the will of the fanatic Athanasius. The hocus-pocus phantasm of a God like another Cerberus, with one body and three heads, had its birth and growth in the blood of thousands and thousands of martyrs. And a strong proof of the solidity of the primitive faith, is its restoration, as soon as a nation arises which vindicates to itself the freedom of religious opinion, and its external divorce from the civil authority. The pure and simple unity of the Creator of the universe, is now all but ascendant in the Eastern States; it is dawning in the West, and advancing towards the South; and I confidently expect that the present generation will see Unitarianism become the general religion of the United States. The Eastern presses are giving us many excellent pieces on the subject, and Priestley's learned writings on it are, or should be, in every hand. In fact, the Athanasian paradox that one is three, and three but one, is so incomprehensible to the human mind, that no candid man can say he has any idea of it, and how can he believe what presents no idea? He who thinks he does, only deceives himself. He proves, also, that man, once surrendering his reason, has no remaining guard against absurdities the most monstrous, and like a ship without a rudder, is the sport of every wind. With such persons gullibility which they call faith, takes the helm from the hand of reason, and the mind becomes a wreck."
"I write with freedom, because while I claim a right to believe in one God, if so my reason tells me, I yield as freely to others that of believing in three. Both religions, I find, make honest men, and that is the only point society has any right to look to. Although this mutual freedom should produce mutual indulgence, yet I wish not to be brought in question before the public on this or any other subject, and I pray you to consider me as writing under that trust. I take no part in controversies, religious or political. At the age of eighty, tranquility is the greatest good of life, and the strongest of our desires that of dying in the good will of all mankind. And with the assurance of all my good will to Unitarian and Trinitarian, to Whig and Tory, accept for yourself that of my entire respect."
----- To W. Short, 1820
The Presbyterian clergy are loudest; the most intolerant of all sects, the most tyrannical and ambitious; ready at the word of the lawgiver, if such a word could be now obtained, to put the torch to the pile, and to rekindle in this virgin hemisphere, the flames in which their oracle Calvin consumed the poor Servetus, because he could not find in his Euclid the proposition which has demonstrated that three are one and one is three, nor subscribe to that of Calvin, that magistrates have a right to exterminate all heretics to Calvinistic Creed. They pant to re-establish, by law that holy inquisition, which they can now only infuse into public opinion. We have most unwisely committed to the hierophants of our particular superstition, the direction of public opinion, that lord of the universe. We have given them stated and privileged days to collect and catechise us, opportunities of delivering their oracles to the people in mass, and of molding their minds as wax in the hollow of their hands. But in despite of their fuminations against endeavors to enlighten the general mind, to improve the reason of the people, and to encourage them in the use of it, the liberality of this State will support this institution [University of Virginia], and give fair play to the cultivation of reason.