Here are some quotes about and related to critical thinking.

“That which can be asserted without evidence can be dismissed without evidence.” — Christopher Hitchens

“I like to think that the bad ideas I describe […] might someday inspire one of you to come up with actual good ideas. That’s how ideas evolve; you start with bad ones then tweak them. If I may borrow and modify a quote from Isaac Newton: If you can see further it is only because you’re standing on the pile of manure I so generously provided. Bad ideas are the raw materials for good ideas […] One of the big secrets to creativity is that you have to start walking before you decide where you’re going. It’s opposite of how you’re raised to think.” — Scott Adams

“Your system is perfectly designed to give you the results you are currently getting.” — William Edwards Deming

“The highest form of ignorance is when you reject something you don’t know anything about.” — Wayne Dyer

“Humility is not thinking less of yourself, it’s thinking of yourself less.” — Rick Warren

“Clear thinking requires courage rather than intelligence”. — Unknown

“Everyone is wise until he speaks.” — Irish proverb

“Half of being smart is knowing what you’re dumb at.” — David Gerrold

“Learning without thought is labor lost.” — Confucius

“Minds are like parachutes. They only function when they are open.” — Sir James Dewar

“Education’s purpose is to replace an empty mind with an open one.”  — Malcolm S. Forbes

“Thinking about thinking can make you crazy.” — Richard Feynman

“Nothing in the world is more dangerous than sincere ignorance and consciencious stupidity.” — Martin Luther King, Jr.

“In politics, stupidity is not a handicap.” — Napoleon Bonaparte

“Stupidity is the same as evil if you judge by results.” — Margaret Atwood

“The only victories which leave no regret are those gained over ignorance.” — Napoleon Bonaparte

“Those who never retract their opinions love themselves more than they love truth.” — Joseph Joubert

“If stupidity got us into this mess, why can’t it get us out?” — Will Rogers

“I don’t want to elect anyone stupid enough to want the job.” — Erma Bombeck

“I do not believe in the collective wisdom of individual ignorance.” — Thomas Carlyle

“Stupidity is the friend of evil.” — Unknown

“It is not enough to have a good mind; the main thing is to use it well.”  — Rene Descartes

“Knowing a great deal is not the same as being smart; intelligence is not information alone but also judgment, the manner in which information is collected and used.” — Carl Sagan

“Truly great madness cannot be achieved without significant intelligence.” — Henrik Tikkanen

“The sign of an intelligent people is their ability to control their emotions by the application of reason.” — Marya Mannes

“An intelligent person is one whose mind watches itself.” — Unknown

“I not only use all the brains that I have, but all that I can borrow.” — Woodrow Wilson

“It is better to have a fair intellect that is well used than a powerful one that is idle.” — Bryant H. McGill

“The best intelligence test is what we do with our leisure.” — Laurence J. Peter

“It is impossible to underrate human intelligence – beginning with one’s own.” — Henry B. Adams

“A conclusion is the place where you got tired of thinking.” — Unknown (seems to be attributed to many different people)

“Everyone is gifted. Some open the package sooner.” — Unknown

“Getting lost teaches you how to read a map.” — Cynthia Copeland Lewis

“The man who makes no mistakes does not usually make anything.” — 19th century U.S. diplomat Edward John Phelps

“The beauty of doing nothing is that you can do it perfectly. Only when you do something is it almost impossible to do it without mistakes. Therefore people who are contributing nothing to society except their constant criticisms can feel both intellectually and morally superior.” — Thomas Sowell

“Reference to a thinker’s bias is no substitute for a refutation of his doctrines by tenable arguments. Those who charge the economists with bias merely show that they are at a loss to refute their teachings by critical analysis.” — Ludwig von Mises. [This applies to everyone, though, not just economists.]

“In theory, there is no difference between theory and practice. In practice, there is.” — Yogi Berra

“It is usually futile to try to talk facts and analysis to people who are enjoying a sense of moral superiority in their ignorance.” — Thomas Sowell

“Unanswered questions are far less dangerous than unquestioned answers.” — Unknown

“When choosing a leader, we always kept in mind that humility provides clarity where arrogance makes a cloud. The last thing we wanted was to be led by someone whose judgment and actions were clouded by arrogance.” — The Lakota Way