“Philosophical problems can be compared to locks on safes, which can be opened by dialing a certain word or number, so that no force can open the door until just this word has been hit upon, and once it is hit upon any child can open it.”

“The main problem with many nonscientific world models is the vigor with which they insist upon their rightness. Once a world model claims to be completely right, it is no longer open to any changes. …Closed systems can be comforting, but they are limited. …It's not the best we can do. Neither is extreme "open-mindednesss" that slides into "empty headedness"—the ideal that we can never really know anything.”

“No one can really help you. No one can open your doors. You locked them up, and only you can open them. When you open any door, beyond it you find others standing there who had passed you long ago, but now, unable to proceed, they are there waiting; others are there waiting for you. Then you come, and, opening a door, those waiting disciples perhaps may pass on; thus on and on. What a privilege this, to reflect that we may perhaps be able to help those who seemed greater than ourselves!”

“Knowledge was not meant to be locked behind doors. It breathes best in the open air where all men can inhale its essence.”

“The mere fact that a thought or idea can be expressed articulately in words involves that it is still open to question; and the mere fact that a difficulty can be definitely conceived involves that it is open to solution.”

“Presidents and Congresses, laws and lawsuits can open the doors to the polling places and open the doors to the wondrous rewards which await the wise use of the ballot. But only the individual Negro, and all others who have been denied the right to vote, can really walk through those doors, and can use that right, and can transform the vote into an instrument of justice and fulfillment.”

“If you can hit a guy once, you can hit him twice.”

“The doors of the world are opened to people who can read.”

“All that we can gain in the west depends on the Entente — on the extent to which it may wish to squeeze Germany, [while in the east] there are doors that open and close, and it depends on who forces them open and how far.”

“Imagination, of course, can open any door - turn the key and let terror walk right in.”