“When the subject is strong, simplicity is the only way to treat it.” 

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

“All tyranny needs to gain a foothold is for people of good conscience to remain silent.”

“Our properties within our own territories [should not] be taxed or regulated by any power on earth but our own.”

“I'm a greater believer in luck, and I find the harder I work the more I have of it”

“Some men look at constitutions with sanctimonious reverence and deem them like the ark of the covenant, too sacred to be touched. They ascribe to the men of the preceding age a wisdom more than human and suppose what they did to be beyond amendment”

“...it is not to be understood that I am with him [Jesus] in all his doctrines. I am a Materialist, he takes the side of spiritualism; he preaches the efficacy of repentance toward forgiveness of sin. I require a counterpoise of good works to redeem it... Among the sayings & discourses imputed to him by his biographers, I find many passages of fine imagination, correct morality, and of the most lovely benevolence: and others again of so much ignorance, so much absurdity, so much untruth, charlatanism, and imposture, as to pronounce it impossible that such contradictions should have proceeded from the same being.

“The pretense that the workings of the mind, like the actions of the body, are subject to the control of laws, does not seem sufficiently demolished. ... The legitimate powers of government extend to such acts only as are injurious to others.”

“Good humor is one of the preservatives of our peace and tranquility” 

“A habilidade mais valiosa é aquela de jamais usar duas palavras quando uma apenas basta.”

“Those who expect to be both ignorant and free, expect what never was and never will be.” 

“You have heard of the new chemical nomenclature endeavored to be introduced by Lavoisier, Fourcroy, &c. Other chemists of this country, of equal note, reject it, and prove in my opinion that it is premature, insufficient and false. These latter are joined by the British chemists; and upon the whole, I think the new nomenclature will be rejected, after doing more harm than good. There are some good publications in it, which must be translated into the ordinary chemical language before they will be useful.”

“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.”

“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]” 

“With your talents and industry, with science, and that steadfast honesty, which eternally pursues right, regardless of consequences, you may promise yourself everything but health, without which there is no happiness.”