“I [am] obliged to recur ultimately to my habitual anodyne, "I feel: therefore I exist." I feel bodies which are not myself: there are other existencies then. I call them "matter". I feel them changing place. This gives me "motion". Where there is an absence of matter, I call it "void", or "nothing", or "immaterial space". On the basis of sensation, of matter and motion, we may erect the fabric of all the certainties we can have or need.” 

“There is not a truth existing which I fear, or would wish unknown to the whole world.”

“I agree with yours of the 22d that a professorship of Theology should have no place in our institution. but we cannot always do what is absolutely best. those with whom we act, entertaining different views, have the power and the right of carrying them into practice. truth advances, & error recedes step by step only; and to do to our fellow-men the most good in our power, we must lead where we can, follow where we cannot, and still go with them, watching always the favorable moment for helping them to another step.

“The bill for establishing religious freedom, the principles of which had, to a certain degree, been enacted before, I had drawn in all the latitude of reason & right. It still met with opposition; but, with some mutilations in the preamble, it was finally passed; and a singular proposition proved that it's protection of opinion was meant to be universal. Where the preamble declares that coercion is a departure from the plan of the holy author of our religion, an amendment was proposed, by inserting the word "Jesus Christ," so that it should read "a departure from the plan of Jesus Christ, the holy author of our religion." The insertion was rejected by a great majority, in proof that they meant to comprehend, within the mantle of it's protection, the Jew and the Gentile, the Christian and Mahometan, the Hindoo, and infidel of every denomination.”

“I set out on this ground, which I suppose to be self-evident, that the earth belongs in usufruct to the living.”

“Another means of silently lessening the inequality of property is to exempt all from taxation below a certain point, and to tax the higher portions or property in geometrical progression as they rise. Whenever there are in any country uncultivated lands and unemployed poor, it is clear that the laws of property have been so far extended as to violate natural right. The earth is given as a common stock for man to labor and live on.

“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. I knew that age well; I belonged to it, and labored with it. It deserved well of its country. It was very like the present, but without the experience of the present; and forty years of experience in government is worth a century of book-reading; and this they would say themselves, were they to rise from the dead. I am certainly not an advocate for frequent and untried changes in laws and constitutions. I think moderate imperfections had better be borne with; because, when once known, we accommodate ourselves to them, and find practical means of correcting their ill effects. But I know also, that laws and institutions must go hand in hand with the progress of the human mind. As that becomes more developed, more enlightened, as new discoveries are made, new truths disclosed, and manners and opinions change with the change of circumstances, institutions must advance also, and keep pace with the times. We might as well require a man to wear still the coat which fitted him when a boy, as civilized society to remain ever under the regimen of their barbarous ancestors.” 

“The most fortunate of us, in our journey through life, frequently meet with calamities and misfortunes which may greatly afflict us; and, to fortify our minds against the attacks of these calamities and misfortunes, should be one of the principal studies and endeavours of our lives.”

“We took the liberty to make some enquiries concerning the ground of their pretensions to make war upon nations who had done them no injury, and observed that we considered all mankind as our friends who had done us no wrong, nor had given us any provocation. The Ambassador [of Tripoli] answered us that it was founded on the Laws of their Prophet, that it was written in their Koran, that all nations who should not have acknowledged their authority were sinners, that it was their right and duty to make war upon them wherever they could be found, and to make slaves of all they could take as Prisoners, and that every Musselman who should be slain in battle was sure to go to Paradise.

“Nothing is more likely than that [the] enumeration of powers is defective. This is the ordinary case of all human works. Let us then go on perfecting it by adding by way of amendment to the Constitution those powers which time and trial show are still wanting”

“A strong body makes the mind strong. As to the species of exercises, I advise the gun. While this gives moderate exercise to the body, it gives boldness, enterprise and independence to the mind. Games played with the ball and others of that nature are too violent for the body and stamp no character on the mind. Let your gun therefore be your constant companion of your walks.”

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

“Bigotry is the disease of ignorance, of morbid minds; enthusiasm of the free and buoyant. Education and free discussion are the antidotes of both. We are destined to be a barrier against the returns of ignorance and barbarism. Old Europe will have to lean on our shoulders, and to hobble along by our side, under the monkish trammels of priests and kings, as she can. What a Colossus shall we be when the Southern continent comes up to our mark! What a stand will it secure as a ralliance for the reason & freedom of the globe! I like the dreams of the future better than the history of the past. So good night. I will dream on, always fancying that Mrs Adams and yourself are by my side marking the progress and the obliquities of ages and countries.”

“The care of human life and happiness, and their destruction is the first and only legitimate object of a good government.”

“I cannot live without books . . .”