"Chesterton's Fence":
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."
Quoted by Cory Doctorow
-- @pluralistic