“We can judge our progress by the courage of our questions and the depth of our answers, our willingness to embrace what is true rather than what feels good.”

Source: Cosmos (1980), p. 193

Special Message to the Congress on Education (20 February 1961) http://www.jfklink.com/speeches/jfk/publicpapers/1961/jfk46_61.html
1961
Context: Our progress as a nation can be no swifter than our progress in education. Our requirements for world leadership, our hopes for economic growth, and the demands of citizenship itself in an era such as this all require the maximum development of every young American's capacity. The human mind is our fundamental resource.

Variant: We are more severe judges of our own acts... We judge our thoughts, our intents, our secret curses, our secret hates, not only our acts.
Source: A Spy in the House of Love

(XIV.3) Del Rey, p. 472
Blade of Tyshalle (2001)

Presidential campaign (April 12, 2015 – 2016), 2016 Democratic National Convention (July 28, 2016)
Context: My friends, we've come to Philadelphia – the birthplace of our nation – because what happened in this city 240 years ago still has something to teach us today. We all know the story. But we usually focus on how it turned out - and not enough on how close that story came to never being written at all. When representatives from 13 unruly colonies met just down the road from here, some wanted to stick with the King. Some wanted to stick it to the king, and go their own way. The revolution hung in the balance. Then somehow they began listening to each other … compromising … finding common purpose. And by the time they left Philadelphia, they had begun to see themselves as one nation. That's what made it possible to stand up to a King. That took courage. They had courage. Our Founders embraced the enduring truth that we are stronger together. America is once again at a moment of reckoning. Powerful forces are threatening to pull us apart. Bonds of trust and respect are fraying. And just as with our founders, there are no guarantees. It truly is up to us. We have to decide whether we all will work together so we all can rise together.

2014, Address to European Youth (March 2014)

Journal entry (21 July 1944); later published in The Wartime Journals (1970)
Context: The intense artillery fire has stripped the trees of leaves and branches so that the outline of the coral ridge itself can be seen silhouetted against the sky. Since I have been on Owi Island, at irregular intervals through the night and day, the sound of our artillery bombarding this Japanese stronghold has floated in across the water. This afternoon, I stood on the cliff outside our quarters (not daring to sit on the ground because of the danger of typhus) and watched the shells bursting on the ridge. For weeks that handful of Japanese soldiers, variously estimated at between 250 and 700 men, has been holding out against overwhelming odds and the heaviest bombardment our well-supplied guns can give them.
If positions were reversed and our troops held out so courageously and well, their defense would be recorded as one of the most glorious examples of tenacity, bravery, and sacrifice in the history of our nation. But, sitting in the security and relative luxury of our quarters, I listen to American Army officers refer to these Japanese soldiers as "yellow sons of bitches." Their desire is to exterminate the Jap ruthlessly, even cruelly. I have not heard a word of respect or compassion spoken of our enemy since I came here.
It is not the willingness to kill on the part of our soldiers which most concerns me. That is an inherent part of war. It is our lack of respect for even the admirable characteristics of our enemy — for courage, for suffering, for death, for his willingness to die for his beliefs, for his companies and squadrons which go forth, one after another, to annihilation against our superior training and equipment. What is courage for us is fanaticism for him. We hold his examples of atrocity screamingly to the heavens while we cover up our own and condone them as just retribution for his acts.