Chesterton's Fence

British writer and critic G.K. Chesterton introduced the metaphor in his 1929 book The Thing, in a passage arguing against reformers who dismantle institutions without understanding why they were built. His example: a fence across a road. A naive reformer, seeing no obvious purpose, tears it down — but Chesterton argues that no one should remove it until they understand why it was erected. The principle anticipates ideas later formalized in systems thinking and the precautionary principle, and entered technology and policy discourse in the 21st century as a rebuke to reflexive "disruption."