“It is neither wealth nor splendor, but tranquility and occupation which give happiness.”

“All, all dead: and ourselves left alone amidst a new generation whom we know not, and who know not us.”

“Later, he told his nephew that religion required careful thought, not reflexive acceptance. "Fix reason firmly in her seat, and call to her tribunal every fact, every opinion. Question with boldness even the existence of a God; because, if there be one, he must more approve the homage of reason, than that of blindfolded fear”

“Importation of such Persons as any of the States now existing shall think proper to admit, shall not be prohibited by the Congress prior to the Year one thousand eight hundred”

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

“I have sworn upon the altar of god, eternal hostility against every form of tyranny over the mind of man.”

“This is the fourth?

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

“...never [enter] into dispute or argument with another. I never saw an instance of one of two disputants convincing the other by argument. I have seen many, on their getting warm, becoming rude, & shooting one another. ... 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? ... There are two classes of disputants most frequently to be met with among us. The first is of young students, just entered the threshold of science, with a first view of its outlines, not yet filled up with the details & modifications which a further progress would bring to their knoledge. The other consists of the ill-tempered & rude men in society, who have taken up a passion for politics. ... Consider yourself, when with them, as among the patients of Bedlam, needing medical more than moral counsel. Be a listener only, keep within yourself, and endeavor to establish with yourself the habit of silence, especially on politics. In the fevered state of our country, no good can ever result from any attempt to set one of these fiery zealots to rights, either in fact or principle. They are determined as to the facts they will believe, and the opinions on which they will act. Get by them, therefore, as you would by an angry bull; it is not for a man of sense to dispute the road with such an animal.”

“I consider him [Alexander von Humboldt] the most important scientist whom I have met.”

“He who permits himself to tell a lie once, finds it much easier to do it the second time.”

“All that is necessary for a student is access to a library.”

“Kalau marah, berhitunglah sampai sepuluh sebelum berbicara, atau bahkan seratus kalau sedang marah sekali.” 

“The dead should not rule the living.”

“I have lived temperately, eating little animal food, and that not as an aliment, so much as a condiment for the vegetables, which constitute my principal diet.”