“The dead should not rule the living.”

“we commit honest maniacs to Bedlam, so judges should be withdrawn from their bench, whose erroneous biases are leading us to dissolution.”

“Reason and free inquiry are the only effectual agents against error.”

“The object most interesting to me for the residue of my life, will be to see you both developing daily those principles of virtue and goodness which will make you valuable to others and happy in yourselves, and acquiring those talents and that degree of science which will guard you at all times against ennui, the most dangerous poison of life. A mind always employed is always happy. This is the true secret, the grand recipe for felicity....In a world which furnishes so many employments which are useful, and so many which are amusing, it is our own fault if we ever know what ennui is...”

“He has erected a multitude of New Offices, and sent hither swarms of Officers to harass our People, and eat out their substance.”

“They (religions) dread the advance of science as witches do the approach of daylight and scowl on the fatal harbinger announcing the subversions of the duperies on which they live.”

“The probable accumulation of the surpluses of revenue beyond what can be applied to the payment of the public debt... merits the consideration of Congress. Shall it lie unproductive in the public vaults?...Or shall it rather be appropriated to the improvements of roads, canals, rivers, education, and other great foundations of prosperity and union”

“I am increasingly persuaded that the earth belongs exclusively to the living and that one generation has no more right to bind another to it's laws and judgments than one independent nation has the right to command another.”

“Follow truth wherever it may lead you.”

“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]” 

“Were I to undertake to answer the calumnies of the newspapers, it would be more than all my own time, and that of 20 aids could effect. For while I should be answering one, twenty new ones would be invented. I have thought it better to trust the justice of my country-men, that they would judge me by what they see of my conduct on the stage where they have placed me.”

“The contest is not between Us and Them, but between Good and Evil, and if those who would fight Evil adopt the ways of Evil, Evil wins.”

“Men have differed in opinion, and been divided into parties by these opinions, from the first origin of societies; and in all governments where they have been permitted freely to think and to speak. the same political parties which now agitate the U.S. have existed through all time. Whether the power of the people, or that of the (best men; nobles) should prevail, were questions which kept the states of Greece and rome in eternal convulsions...” 

“You seem to consider the judges as the ultimate arbiters of all constitutional questions; a very dangerous doctrine indeed, and one which would place us under the despotism of an oligarchy. Our judges are as honest as other men, and not more so. They have, with others, the same passions for party, for power, and the privilege of their corps.... Their power [is] the more dangerous as they are in office for life, and not responsible, as the other functionaries are, to the elective control. The Constitution has erected no such single tribunal, knowing that to whatever hands confided, with the corruptions of time and party, its members would become despots. It has more wisely made all the departments co-equal and co-sovereign within themselves.” 

“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.”