“At school, new ideas are thrust at you every day. Out in the world, you'll have to find your inner motivation to seek for new ideas on your own.”

2015, Remarks to the People of Africa (July 2015)
Context: I have to also say that Africa’s democratic progress is also at risk when leaders refuse to step aside when their terms end. […] When a leader tries to change the rules in the middle of the game just to stay in office, it risks instability and strife -- as we’ve seen in Burundi. And this is often just a first step down a perilous path. And sometimes you’ll hear leaders say, well, I'm the only person who can hold this nation together. If that's true, then that leader has failed to truly build their nation. […] Nobody should be president for life. And your country is better off if you have new blood and new ideas. I'm still a pretty young man, but I know that somebody with new energy and new insights will be good for my country. It will be good for yours, too, in some cases.

"Creativity in Science and Engineering", Martin Perl's blog Reflections on Physics … from the Tau to Dark Energy http://martinperl.com/
Essay on Creativity in Science and Engineering

Lecture June 8, 1958 Nature's Portals of Instruction
Nature

as quoted in Directing the Film, Ed Sherman, 1976.

1950s, Loving Your Enemies (November 1957)
Context: There is something within all of us that causes us to cry out with Ovid, the Latin poet, "I see and approve the better things of life, but the evil things I do." There is something within all of us that causes us to cry out with Plato that the human personality is like a charioteer with two headstrong horses, each wanting to go in different directions. There is something within each of us that causes us to cry out with Goethe, "There is enough stuff in me to make both a gentleman and a rogue." There is something within each of us that causes us to cry out with Apostle Paul, "I see and approve the better things of life, but the evil things I do." So somehow the "isness" of our present nature is out of harmony with the eternal "oughtness" that forever confronts us. And this simply means this: That within the best of us, there is some evil, and within the worst of us, there is some good. When we come to see this, we take a different attitude toward individuals. The person who hates you most has some good in him; even the nation that hates you most has some good in it; even the race that hates you most has some good in it. And when you come to the point that you look in the face of every man and see deep down within him what religion calls "the image of God," you begin to love him in spite of. No matter what he does, you see God’s image there. There is an element of goodness that he can never sluff off. Discover the element of good in your enemy. And as you seek to hate him, find the center of goodness and place your attention there and you will take a new attitude.

Teaching Thinking (1991)

John Nuveen, as quoted in The Leadership Secrets of Billy Graham (2005) by Marshall Shelley, p. 303
Misattributed