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 the 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 scuttle fish, thro’ the element in which they move, and making it impenetrable to the eye of a pursuing enemy. And there they will skulk, until some rational creed can occupy the void which the obliteration of their duperies would leave in the minds of our honest and unsuspecting brethren.

Thomas Jefferson, letter to Francis van der Kemp, August 6, 1816

They observe that on ignition of the needle or spring, Their magnetism and elasticity cease. So on dissolution of the material organ by death it’s action of thought may cease also. And that nobody supposes that the magnetism or elasticity retire to hold a substantive and distinct existence. These were the qualities only of particular conformations of matter: change the conformation, and it’s qualities change also. …… Were it necessary however to form an opinion, I confess I should, with Mr. Locke, prefer swallowing one incomprehensibility rather than two. It requires one effort only to admit the single incomprehensibility of matter endowed with thought: and two to believe, 1st. that of an existence called Spirit, of which we have neither evidence nor idea, and then 2dly. how that spirit which has neither extension nor solidity, can put material organs into motion. These are things which you and I may perhaps know ere long.

Thomas Jefferson, letter to John Adams, March 14, 1820

No man on earth has less taste or talent for criticism than myself, and least and last of all should I undertake to criticise works on the Apocalypse. It is between 50. and 60. years since I read it, and I then considered it as merely the ravings of a Maniac, no more worthy, nor capable of explanation than the incoherences of our own nightly dreams. …… There is not coherence enough in them to countenance any suite of rational ideas. You will judge therefore from this how impossible I think it that either your explanation, or that of any man in the heavens above, or on the earth beneath, can be a correct one. What has no meaning admits no explanation.

Thomas Jefferson, letter to Alexander Smyth, January 17, 1825

In every country and every age the priest has been hostile to liberty. He is always in alliance with the despot abetting his abuses in return for protection to his own. It is easier to acquire wealth and power by this combination than by deserving them: and to effect this they have perverted the purest religion ever preached to man, into mystery and jargon unintelligible to all mankind and therefore the safer engine for their purposes.

Thomas Jefferson, letter to Horatio Spafford, March 17, 1814

The most undesirable of all things is a long life and there is nothing I have ever dreaded so much. Altho’ subject to occasional indispositions my health is too good generally to give me fear on that subject. I am weak indeed in body, able scarcely to walk into my garden without too much fatigue, but a ride of 6, 8, or 10 miles a day gives me none. Still however a start or stumble of my horse or some one of the accidents which constantly beset us, may cut short the thread of life and relieve me from the evils of dotage. Come when it will it will find me neither unready nor unwilling.

Thomas Jefferson, letter to Benjamin Waterhouse, January 8, 1825

That form [of government] which we have substituted, restores the free right to the unbounded exercise of reason and freedom of opinion. All eyes are opened, or opening, to the rights of man. The general spread of the light of science has already laid open to every view the palpable truth, that the mass of mankind has not been born with saddles on their backs, nor a favored few booted and spurred, ready to ride them legitimately, by the grace of God. These are grounds of hope for others. For ourselves, let the annual return of this day [July 4] forever refresh our recollections of these rights, and an undiminished devotion to them.

Thomas Jefferson, letter (his last) to Roger Weightman, June 24, 1826

Jefferson had received an invitation to Fourth of July festivities in Washington, for the 50th anniversary of American independence. He was too old and ill, and declined. He died on July 4, 1826.

Calvinism has introduced into the Christian religion more new absurdities than it’s leader had purged it of old ones.

Thomas Jefferson, letter to Salma Hale, July 26, 1818

Yes, I saw the apostrophe. It’s original.

Experience declares that man is the only animal which devours his own kind, for I can apply no milder term to the governments of Europe, and to the general prey of the rich on the poor.

Thomas Jefferson, letter to Edward Carrington, January 16, 1787

I am not myself apt to be alarmed at innovations recommended by reason. That dread belongs to those whose interests or prejudices shrink from the advance of truth and science.

Thomas Jefferson, letter to Dr. John Manners, February 22, 1814

The Christian priesthood, finding the doctrines of Christ levelled to every understanding, and too plain to need explanation, saw, in the mysticisms of Plato, materials with which they might build up an artificial system which might, from its indistinctness, admit everlasting controversy, give employment for their order, and introduce it to profit, power and preeminence. The doctrines which flowed from the lips of Jesus himself are within the comprehension of a child; but thousands of volumes have not yet explained the Platonisms engrafted on them: and for this obvious reason that nonsense can never be explained.

Thomas Jefferson, letter to John Adams, July 5, 1814