“Honesty is the first chapter in the book of wisdom.” 

“He who knows nothing is closer to the truth than he whose mind is filled with falsehoods and errors.”

“In matters of principal stand like a rock.”

“I am certainly not an advocate for frequent and untried changes in laws and constitutions...but I know also that laws and constitutions must go hand in hand with the progress of the human mind.....”

“I am conscious that an equal division of property is impracticable. But the consequences of this enormous inequality [in Europe] producing so much misery to the bulk of mankind, legislators cannot invent too many devices for subdividing property,...[One] means of silently lessening the inequality of property is to exempt all from taxation below a certain point, and to tax the higher portions of property in geometrical progression as they rise.”

“When I hear another express an opinion which is not mine, I say to myself, he has a right to his opinion, as I to mine. Why should I question it? His error does me no injury, and shall I become a Don Quixote, to bring all men by force of argument to one opinion? ...Be a listener only, keep within yourself, and endeavor to establish with yourself the habit of silence, especially in politics.”

“To your request of my opinion of the manner in which a newspaper should be conducted, so as to be most useful, I should answer, ‘by restraining it to true facts & sound principles only.’ Yet I fear such a paper would find few subscribers. It is a melancholy truth, that a suppression of the press could not more compleatly deprive the nation of its benefits, than is done by its abandoned prostitution to falsehood. Nothing can now be believed which is seen in a newspaper. Truth itself becomes suspicious by being put into that polluted vehicle. The real extent of this state of misinformation is known only to those who are in situations to confront facts within their knolege with the lies of the day. I really look with commiseration over the great body of my fellow citizens, who, reading newspapers, live & die in the belief, that they have known something of what has been passing in the world in their time; whereas the accounts they have read in newspapers are just as true a history of any other period of the world as of the present, except that the real names of the day are affixed to their fables. General facts may indeed be collected from them, such as that Europe is now at war, that Bonaparte has been a successful warrior, that he has subjected a great portion of Europe to his will, &c., &c.; but no details can be relied on. I will add, that the man who never looks into a newspaper is better informed than he who reads them; inasmuch as he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. He who reads nothing will still learn the great facts, and the details are all false.” —Letter to John Norvell, 14 June 1807 [Works 10:417--18]” 

“That liberty [is pure] which is to go to all, and not to the few or the rich alone. (to Horatio Gates, 1798)”

“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.

“Commerce with all nations, alliance with none, should be our motto.”

“I haven't failed. I've just found 10,000 ways that don't work.”

“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 forever refresh our recollection of these rights, and an undiminished devotion to them.”

“If the present Congress errs in too much talking, how can it be otherwise in a body to which the people send 150. lawyers, whose trade it is to question everything, yield nothing, & talk by the hour? That 150. lawyers should do business together ought not to be expected. But to return again to our subject.” 

“Never spend your money before you have earned it.”

“The opinions of men are not the object of civil government, nor under its jurisdiction.”