“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.” 

“Determine never to be idle. No person will have occasion to complain of the want of time, who never loses any. It is wonderful how much may be done, if we are always doing.”

“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.”

“When the people fear the government there is tyranny, when the government fears the people there is liberty.”

“Do you want to know who you are? Don't ask. Act! Action will delineate and define you.”

“I like a little rebellion now and then. It is like a storm in the atmosphere.”

“No government ought to be without censors; and where the press is free no one ever will.”

“There is a natural aristocracy among men. The grounds of this are virtue and talents.”

“...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.”

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

“He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me.” 

“Pride costs us more than hunger, thirst, and cold.”

“A coward is much more exposed to quarrels than a man of spirit.”

“Cultivators of the earth are the most valuable citizens. They are the most vigorous, the most independent, the most virtuous, and they are tied to their country and wedded to its liberty and interests by the most lasting bonds.”