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

“Ridicule is the only weapon which can be used against unintelligible propositions.”

“The equal rights of man, and the happiness of every individual, are now acknowledged to be the only legitimate objects of government.”

“Do not be too severe upon the errors of the people, but reclaim them by enlightening them.”

“...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.”

“The attempt of Lavoisier to reform chemical nomenclature is premature. One single experiment may destroy the whole filiation of his terms; and his string of sulphates, sulphites, and sulphures, may have served no end than to have retarded the progress of science by a jargon, from the confusion of which time will be requisite to extricate us.” 

“I have often thought that nothing would do more extensive good at small expense than the establishment of a small circulating library in every county, to consist of a few well-chosen books, to be lent to the people of the country under regulations as would secure their safe return in due time.”

“Nothing can stop the man with the right mental attitude from achieving his goal. Nothing on earth can help the man with the wrong attitude.”

“Our civil rights have no dependence on our religious opinions any more than our opinions in physics or geometry...”

“I am not an advocate for frequent changes in laws and Constitutions. But 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 discovered and manners and opinions change, with the change of circumstances, institutions must advance also to 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.”