"Chesterton's Fence" is a heuristic used to illustrate the importance of second-order thinking. The name of the heuristic is a reference to a passage from G. K. Chesteron:
There exists in such a case a certain institution or law; let us say, for the sake of simplicity, 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.
Chesterton's Fence suggests the importance of thinking through the second-order consequences of our actions. In other words, what are the consequences of the consequences of our decisions? Chesterton tells us not to remove a fence unless we know why it was put there in the first place. There may have been a good reason.
The original context of the quote is from The Thing, Chesterton's 1929 defense of Catholicism; it's very much a classically conservative argument, an admonition against reformers who, from Chesterton's point of view, demand change from a position of ignorance. Yet, as Rory Sutherland implies, it's advice that may be worth keeping in mind in the age of Silicon Valley and its insatiable appetite for disruption.
Parrish, Shane. “Chesterton’s Fence: A Lesson in Second Order Thinking.” Farnam Street (blog), March 9, 2020. https://fs.blog/2020/03/chestertons-fence/.
Sutherland, Rory. “Watch out for Chesterton’s Fences." The Spectator. Accessed October 24, 2020. https://www.spectator.co.uk/article/watch-out-for-chesterton-s-fences.