“...The Presidential election has given me less anxiety than I myself could have imagined. The next administration will be a troublesome one, to whomsoever it falls, and our John has been too much worn to contend much longer with conflicting factions. I call him our John, because, when you were at the Cul de sac at Paris, he appeared to me to be almost as much your boy as mine....As to the decision of your author, though I wish to see the book {Flourens’s Experiments on the functions of the nervous system in vertebrated animals}, I look upon it as a mere game at push-pin. Incision-knives will never discover the distinction between matter and spirit, or whether there is any or not. That there is an active principle of power in the universe, is apparent; but in what substance that active principle resides, is past our investigation. The faculties of our understanding are not adequate to penetrate the universe. Let us do our duty, which is to do as we would be done by; and that, one would think, could not be difficult, if we honestly aim at it.Your university is a noble employment in your old age, and your ardor for its success does you honor; but I do not approve of your sending to Europe for tutors and professors. I do believe there are sufficient scholars in America, to fill your professorships and tutorships with more active ingenuity and independent minds than you can bring from Europe. The Europeans are all deeply tainted with prejudices, both ecclesiastical and temporal, which they can never get rid of. They are all infected with episcopal and presbyterian creeds, and confessions of faith. They all believe that great Principle which has produced this boundless universe, Newton’s universe and Herschel’s universe, came down to this little ball, to be spit upon by Jews. And until this awful blasphemy is got rid of, there never will be any liberal science in the world.I salute your fireside with best wishes and best affections for their health, wealth and prosperity.{Letter to Thomas Jefferson, 22 January, 1825}”

“We think ourselves possessed, or at least we boast that we are so, of liberty of conscience on all subjects and of the right of free inquiry and private judgment in all cases, and yet how far are we from these exalted privileges in fact. There exists, I believe, throughout the whole Christian world, a law which makes it blasphemy to deny, or to doubt the divine inspiration of all the books of the Old and New Testaments, from Genesis to Revelations. In most countries of Europe it is punished by fire at the stake, or the rack, or the wheel. In England itself, it is punished by boring through the tongue with a red-hot poker. In America it is not much better; even in our Massachusetts, which, I believe, upon the whole, is as temperate and moderate in religious zeal as most of the States, a law was made in the latter end of the last century, repealing the cruel punishments of the former laws, but substituting fine and imprisonment upon all those blasphemies upon any book of the Old Testament or New. Now, what free inquiry, when a writer must surely encounter the risk of fine or imprisonment for adducing any arguments for investigation into the divine authority of those books? Who would run the risk of translating Volney's Recherches Nouvelles? Who would run the risk of translating Dupuis? But I cannot enlarge upon this subject, though I have it much at heart. I think such laws a great embarrassment, great obstructions to the improvement of the human mind. Books that cannot bear examination, certainly ought not to be established as divine inspiration by penal laws... but as long as they continue in force as laws, the human mind must make an awkward and clumsy progress in its investigations. I wish they were repealed.{Letter to Thomas Jefferson, January 23, 1825}”

“Admire and adore the Author of the telescopic universe, love and esteem the work, do all in your power to lessen ill, and increase good, but never assume to comprehend.”

“The Catholic chruch as threatened your life - do you not want revenge? Have you not sold your hatred to the Pretestant cause to work against the church that has hunted you?""No," I said simply. "I hate no one. I want only to be left in peace to understand the mysteries of the universe in my own way.""God has already laid out for us the mysteries of the universe, or as much as He permits us to understand. You think your way is better?""Better than these wars of dogma that have led men to burn and fillet one another across Europe for fifty years? Yes, I do.""Then what is it you believe?"I looked at him. "I believe that, in the end, even the devils will be pardoned.”

“To believe that someone else is responsible for your emotional state is to give them a sort of psychic power over you they do not have...we really do generate our own feelings. No one else can do it for us. We respond and are responsible. To think other people are responsible for our feelings is to inhabit a billiard ball, inanimate universe.”

“I do not believe that Mr. Jefferson ever hated me. On the contrary, I believe he always like me: but he detested Hamilton and by whole administration. Then he wished to be President of the United States, and I stood in his way. So he did everything that he could to pull me down. But if I should quarral with him for that, I might quarrel with every man I have had anything to do with in life. This is human nature....I forgive all my enemies and hope they may find mercy in Heaven. Mr. Jefferson and I have grown old and retired from public life. So we are upon our ancient terms of goodwill.”

“The human being is only a reed, the most feeble in nature; but this is a thinking reed. It isn't necessary for the entire universe to arm itself in order to crush him; a whiff of vapor, a taste of water, suffices to kill him. But when the universe crushes him, the human being becomes still more noble than that which kills him, because he knows that he is dying, and the advantage that the universe has over him. The universe, it does not have a clue."All our dignity consists, then, in thought. This is the basis on which we must raise ourselves, and not space and time, which we would not know how to fill. Let us make it our task, then, to think well: here is the principle of morality.”