“Don't ever take a fence down until you know the reason why it was put up.”
According to The American Chesterton Society http://www.chesterton.org/qmeister2/19.htm, this quotation is actually a paraphrase by John F. Kennedy http://en.wikipedia.org/wiki/John_F._Kennedy of a passage from The Thing (1929) in which Chesterton made reference to a fence or gate erected across a road: "The more modern type of reformer goes gaily up to it and says, "I don't see the use of this; let us clear it away." To which the more intelligent type of reformer will do well to answer: "If you don't see the use of it, I certainly won't let you clear it away. Go away and think. Then, when you can come back and tell me that you do see the use of it, I may allow you to destroy it."
Misattributed
