“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.” 

“Experience declares that man is the only animal which devours his own kind; for I can apply no milder term to the governments of Europe, and to the general prey of the rich on the poor.”

“Leave all the afternoon for exercise and recreation, which are as necessary as reading. I will rather say more necessary because health is worth more than learning.”

“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.”

“The glow of one warm thought is to me worth more than money.”

“We seem not to perceive that, by the law of nature, one generation is to another as one independent nation is to another.”

“Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong.”

“The most valuable of all talents is that of never using two words when one will do.”

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

“The man who reads nothing at all is better educated than the man who reads nothing but newspapers.”

“If once the people become inattentive to the public affairs, you and I, and Congress and Assemblies, Judges and Governors, shall all become wolves. It seems to be the law of our general nature, in spite of individual exceptions.” 

“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.”

“I wish I was a despot that I might save the noble, the beautiful trees that are daily falling sacrifice to the cupidity of their owners, or the necessity of the poor. The unnecessary felling of a tree, perhaps the growth of centuries, seems to me a crime little short of murder.”

“If you want something you've never had You must be willing to do something you've never done.” 

“Speaking one day to Monsieur de Buffon, on the present ardor of chemical inquiry, he affected to consider chemistry but as cookery, and to place the toils of the laboratory on the footing with those of the kitchen. I think it, on the contrary, among the most useful of sciences, and big with future discoveries for the utility and safety of the human race.”