All schools, all colleges have two great functions: to confer, and to conceal valuable knowledge.

Be careful about reading health books. You may die of a misprint.

Education consists mainly in what we have unlearned.

Every improvement that is put upon the real estate is the result of an idea in somebody's head. The skyscraper is another idea; the railroad is another; the telephone and all those things are merely symbols which represent ideas. An andiron, a wash-tub, is the result of an idea that did not exist before.

Evolution is the law of policies: Darwin said it, Socrates endorsed it, Cuvier proved it and established it for all time in his paper on 'The Survival of the Fittest.' These are illustrious names, this is a mighty doctrine: nothing can ever remove it from its firm base, nothing dissolve it, but evolution.

Experience, the only logic sure to convince a diseased imagination and restore it to rugged health.

Get your facts first, and then you can distort them as much as you please.

I am not one of those who in expressing opinions confine themselves to facts.

I am trying to get the hang of this new fangled writing machine, but I am not making a shining success of it. However, this is the first attempt I have ever made & yet I perceive I shall soon & easily acquire a fine facility in its use. … The machine has several virtues. I belive it will priont faster than I can write. One may lean back in his chair & work it. It piles an awful stack of words on one page. It do't muss things or scatter ink blots around. Of course it saves paper.

I have never let my schooling interfere with my education.

I never could do anything with figures, never had any talent for mathematics, never accomplished anything in my efforts at that rugged study, and to-day the only mathematics I know is multiplication, and the minute I get away up in that, as soon as I reach nine times seven— [He lapsed into deep thought, trying to figure nine times seven. Mr. McKelway whispered the answer to him.] I've got it now. It's eighty-four. Well, I can get that far all right with a little hesitation. After that I am uncertain, and I can't manage a statistic.

I've come loaded with statistics, for I've noticed that a man can't prove anything without statistics. No man can.

If the Eiffel Tower were now representing the world's age, the skin of paint on the pinnacle-knob at its summit would represent man's share of that age; and anybody would perceive that that skin was what the tower was built for.
[Declaiming Alfred Russel Wallace's 'anthropocentric' theory, that the universe was created specifically for the evolution of mankind.]

In the laboratory there are no fustian ranks, no brummagem aristocracies; the domain of Science is a republic, and all its citizens are brothers and equals, its princes of Monaco and its stonemasons of Cromarty meeting, barren of man-made gauds and meretricious decorations, upon the one majestic level!

In the space of one hundred and seventy-six years the Lower Mississippi has shortened itself two hundred and forty-two miles. That is an average of a trifle over one mile and a third per year. Therefore, any calm person, who is not blind or idiotic, can see that in the old Oolitic Silurian Period, must a million years ago next November, the Lower Mississippi River was upward of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing-rod. And by the same token any person can see that seven hundred and forty-two years from now the Lower Mississippi will be only a mile and three-quarters long, and Cairo and New Orleans will have their streets joined together, and be plodding comfortably along under a single mayor and a mutual board of aldermen. There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.

It is curious to reflect on how history repeats itself the world over. Why, I remember the same thing was done when I was a boy on the Mississippi River. There was a proposition in a township there to discontinue public schools because they were too expensive. An old farmer spoke up and said if they stopped the schools they would not save anything, because every time a school was closed a jail had to be built.
It's like feeding a dog on his own tail. He'll never get fat. I believe it is better to support schools than jails.

It is noble to teach oneself, but still nobler to teach others and less trouble.

Medicine has made all its progress during the past fifty years. ... How many operations that are now in use were known fifty years ago?—they were not operations, they were executions.

Scientists have odious manners, except when you prop up their theory; then you can borrow money off them.

Supposing is good, but finding out is better.

That is the way of the scientist. He will spend thirty years in building up a mountain range of facts with the intent to prove a certain theory; then he is so happy with his achievement that as a rule he overlooks the main chief fact of all—that all his accumulation proves an entirely different thing.

That reminds me to remark, in passing, that the very first official thing I did, in my administration—and it was on the first day of it, too—was to start a patent office; for I knew that a country without a patent office and good patent laws was just a crab, and couldn't travel any way but sideways or backways.

The cigar-box which the European calls a 'lift' needs but to be compared with our elevators to be appreciated. The lift stops to reflect between floors. That is all right in a hearse, but not in elevators. The American elevator acts like a man's patent purge—it works.

The fact that man knows right from wrong proves his intellectual superiority to other creatures; but the fact that he can do wrong proves his moral inferiority to any creature that cannot.

Training is everything. The peach was once a bitter almond; cauliflower is nothing but a cabbage with a college education.

You may say organize, organize, organize; but there may be so much organization that it will interfere with the work to be done.