“I feel: therefore I exist. I feel bodies which are not myself: there are other existences then. I call them matter. I feel them changing place. This gives me motion. Where there is an absence of matter, I call it void, or nothing, or immaterial space. On the basis of sensation, of matter and motion, we may erect the fabric of all the certainties we can have or need.”
|In a 1789 letter to American painter John Trumbull, in an order for portraits of Bacon, Locke, and Newton—supposedly arranged as diagrammed (Ѻ) above—Jefferson identified Bacon, Locke, and Newton as "the three greatest men that have ever lived, without any exception". |
“We had no occasion to search into musty records, to hunt up royal parchments, or to investigate the laws and institutions of a semi-barbarous ancestry. We appealed to those of nature and found them engraved on our hearts.”— Thomas Jefferson (1826), on the origin of the Declaration of Independence, shortly before his dereaction (death) 
“Leaving aside examples such as the celebrated influence of Isaac Newton’s mechanics on Thomas Jefferson’s Declaration of Independence, the parallels between physics and literature are simply too evident to ignore.”
|A future “god museum” cartoon, reminiscent of Jefferson’s 1823 letter to John Adams on the future mythological classification of “mystical generation of Jesus”. |
“Religion: your reason is now mature enough [age 17] to examine this object. In examining this subject, divest yourself of all bias, in favor of novelty and singularity of opinion, shake off all fears and servile prejudices, under which weak minds are servilely crouched: fix reason in her seat firmly; question with boldness even the existence of God; because if there is one, he must approve more of the homage of reason than that of blindfolded faith. Read the Bible as you would Tacitus or Livy. Those facts in the Bible which contradict the laws of nature must be examined with care.”— Thomas Jefferson (1787), “Letter to [nephew] Peter Carr” 
“And the day will come when the mystical generation of Jesus, by the supreme being as his father in the womb of a virgin will be classed with the fable of the generation of Minerva in the brain of Jupiter.”— Thomas Jefferson (1823), “Letter to John Adams”, Apr 11 (Ѻ)
“As you say of yourself, I too am an Epicurian. I consider the genuine (not the imputed) doctrines of Epicurus as containing everything rational in moral philosophy which Greece and Rome have left us. Epictetus indeed, has given us what was good of the stoics; all beyond, of their dogmas, being hypocrisy and grimace. Their great crime was in their calumnies of Epicurus and misrepresentations of his doctrines; in which we lament to see the candid character of Cicero engaging as an accomplice. Diffuse, vapid, rhetorical, but enchanting. His prototype Plato, eloquent as himself, dealing out mysticisms incomprehensible to the human mind, has been deified by certain sects usurping the name of Christians; because, in his foggy conceptions, they found a basis of impenetrable darkness whereon to rear fabrications as delirious, of their own invention. These they fathered blasphemously on him whom they claimed as their founder, but who would disclaim them with the indignation which their caricatures of his religion so justly excite.
|Jefferson, who owned five plus volumes of Lucretius’ 55BC On the Nature of Things, was a noted adherent to the works of Epicurus, shown above, describing himself in the years 1819-20 as an "Epicurean materialist" in belief system philosophy.|
Of Socrates we have nothing genuine but in the Memorabilia of Xenophon; for Plato makes him one of his Collocutors merely to cover his own whimsies under the mantle of his name; a liberty of which we are told Socrates himself complained. Seneca is indeed a fine moralist, disfiguring his work at times with some Stoicisms, and affecting too much of antithesis and point, yet giving us on the whole a great deal of sound and practical morality.
But the greatest of all the reformers of the depraved religion of his own country, was Jesus of Nazareth. Abstracting what is really his from the rubbish in which it is buried, easily distinguished by its lustre from the dross of his biographers, and as separable from that as the diamond from the dunghill, we have the outlines of a system of the most sublime morality which has ever fallen from the lips of man; outlines which it is lamentable he did not live to fill up.
Epictetus and Epicurus give laws for governing ourselves, Jesus a supplement of the duties and charities we owe to others. The establishment of the innocent and genuine character of this benevolent moralist, and the rescuing it from the imputation of imposture, which has resulted from artificial systems [N1], invented by ultra-Christian sects, unauthorized by a single word ever uttered by him, is a most desirable object, and one to which Priestley has successfully devoted his labors and learning. It would in time, it is to be hoped, effect a quiet euthanasia of the heresies of bigotry and fanaticism which have so long triumphed over human reason, and so generally and deeply afflicted mankind; but this work is to be begun by winnowing the grain from the chaff of the historians of his life.
A 2011 fence-protected holiday display, by Atheists United, in Santa Monica, California, showing a Jefferson quote on religion a mythology. (Ѻ)
I have sometimes thought of translating Epictetus (for he has never been tolerable translated into English) by adding the genuine doctrines of Epicurus from the Syntagma of Gassendi, and an abstract from the Evangelists of whatever has the stamp of the eloquence and fine imagination of Jesus. The last I attempted too hastily some twelve or fifteen years ago. It was the work of two or three nights only, at Washington, after getting through the evening task of reading the letters and papers of the day. But with one foot in the grave, these are now idle projects for me. My business is to beguile the wearisomeness of declining life, as I endeavor to do, by the delights of classical reading and of mathematical truths, and by the consolations of a sound philosophy, equally indifferent to hope and fear.
I take the liberty of observing that you are not a true disciple of our master Epicurus, in indulging the indolence to which you say you are yielding. One of his canons, you know, was that "the indulgence which prevents a greater pleasure, or produces a greater pain, is to be avoided." Your love of repose will lead, in its progress, to a suspension of healthy exercise, a relaxation of mind, an indifference to everything around you, and finally to a debility of body, and hebetude of mind, the farthest of all things from the happiness which the well-regulated indulgences of Epicurus ensure; fortitude, you know, is one of his four cardinal virtues. That teaches us to meet and surmount difficulties; not to fly from them, like cowards; and to fly, too, in vain, for they will meet and arrest us at every turn of our road. Weigh this matter well; brace yourself up; take a seat with Correa, and come and see the finest portion of your country, which, if you have not forgotten, you still do not know, because it is no longer the same as when you knew it. It will add much to the happiness of my recovery to be able to receive Correa and yourself, and prove the estimation in which I hold you both. Come, too, and see our incipient University, which has advanced with great activity this year. By the end of the next, we shall have elegant accommodations for seven professors, and the year following the professors themselves. No secondary character will be received among them. Either the ablest which America or Europe can furnish, or none at all. They will give us the selected society of a great city separated from the dissipations and levities of its ephemeral insects.
I am glad the bust of Condorcet has been saved and so well placed. His genius should be before us; while the lamentable, but singular act of ingratitude which tarnished his latter days, may be thrown behind us. I will place under this a syllabus of the doctrines of Epicurus [N2] somewhat in the lapidary style, which I wrote some twenty years ago [c.1799], a like one of the philosophy of Jesus, of nearly the same age is too long to be copied. Vale, et tibipersuade carissimum te esse mihi.”
|Left: a photo of Jefferson’s portable writing desk. (Ѻ) Right: a sketch (Ѻ) of Jefferson sitting his "swivel chair", something he invented, drawing out architectural plans for the University of Virginia.|
“I do not believe that the most high will permit a howling atheist to sit at the head of the nation.”— Thomas Robbins (1800), Diary Entry (Ѻ), May 8
“If not an absolute atheist, he had no belief in a future existence. All his ideas of obligation or retribution were bounded by the present life.”— John Quincy Adams (1831), Diary Entry, Jan 11
“Jefferson was, himself, a living and walking encyclopedia.”— William Wirt (1833) (Ѻ)
“Believe me, dear Sir: there is not in the British Empire a man who more cordially loves a union with Great Britain than I do. But, by the god that made me, I will cease to exist before I yield to a connection on such terms as the British Parliament propose; and in this, I think I speak the sentiments of America.”— Thomas Jefferson (1775), “Letter to John Randolph”, Nov 29 
“The legitimate powers of government extend to such acts only as are injurious to others. 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.”— Thomas Jefferson (1782), “Notes on the State of Virginia” (Ѻ)
“I remember well the enthusiasm with which I devoured it [Hume’s work] when young, and the length of time, the research and reflection which were necessary to eradicate the poison [see: unlearn] it had instilled into my mind.”— Thomas Jefferson (1810), “Letter to William Duane”, Aug 12 
“History, I believe, furnishes no example of a priest-ridden people maintaining a free civil government. This marks the lowest grade of ignorance of which their civil as well as religious leaders will always avail themselves for their own purposes.”— Thomas Jefferson (1813), “Letter to Alexander von Humboldt”; in FSM app
“I am of a [religious] sect by myself, as far as I know.”— Thomas Jefferson (1819), “Letter to Ezra Stiles”, Jun 25
“Speaking of Plato, I will add, that no writer, ancient or modern, has bewildered the world with more ignes fatui [misleading influence], than this renowned philosopher, in ethics, in politics, and in physics. In the latter, to specify a single example, compare his views on the animal economy, in his Timaeus, with those of Margaret Bryan in her Conversations on Chemistry, and weigh the science of the canonized philosopher against the good sense of the unassuming lady. But Plato’s versions have furnished a basis for endless systems of ‘mystical theology’, and he is therefore all but adopted as a Christian saint. It is surely time for men to think for themselves, and to throw off the authority of names so artificially magnified.”— Thomas Jefferson (1820), “Letter to William Short”, Aug 4 
“To talk of immaterial existences is to talk of nothings. To say that the human soul, angels, god, are immaterial, is to say they are nothings, or that there is no god, no angels, no soul. I cannot reason otherwise ... without plunging into the fathomless abyss of dreams and phantasms. I am satisfied, and sufficiently occupied with the things which are, without tormenting or troubling myself about those which may in-deed be, but of which I have no evidence.”— Thomas Jefferson (1820), “Letter to John Adams”, Aug 15
“Priests of different sects dread the advance of science as witches do the approach of daylight.”— Thomas Jefferson (1820), “Letter to Correa de Serra”, Apr 11
“I have recently been examining all the known superstitions of the world, and do not find in our particular [Christian] superstition on redeeming feature. They are all alike, founded on fables and mythologies.”— Thomas Jefferson (c.1820), “Letter to Dr. Woods”; not found in extant work; possibly an ad hoc paraphrase as cited by John Remsburg (1883) (Ѻ); cited by James Haught (1996)
|A re-constructed depiction some of the personal library of 6,700+ books owned by Jefferson’s at Monticello.  Note: the reconstructive cataloging of the books owned by Jefferson is what started the Legacy Library project at LibraryThing.com.|