Index

Mental Models

Chesterton's Fence

If you encounter a rule or structure and do not understand its purpose, do not remove it until you do — it was put there for a reason you may not yet see.

Chesterton's Fence prevents costly removals by requiring that you understand the original purpose of a practice or system before eliminating it.

Core question

Why was this put in place, and what problem was it solving that we might recreate by removing it?

Example

A new engineering lead removes a slow integration test suite to speed up deploys. Two weeks later, a production bug slips through that the tests were specifically designed to catch. The fence existed for a reason.

How to apply

  1. 1.Before removing a process, rule, or system, investigate why it was created.
  2. 2.Talk to people who were present when it was introduced.
  3. 3.Identify the specific problem it solved and whether that problem still exists.
  4. 4.Only remove it once you understand the original rationale and have a plan for the gap.

Pitfalls

  • ·Using Chesterton's Fence to block all change and protect outdated practices.
  • ·Confusing understanding the reason with agreeing with the reason — you can understand and still remove.
  • ·Accepting that something must remain because no one remembers why it exists.

Questions

Where does the name Chesterton's Fence come from?

G.K. Chesterton proposed a thought experiment: if you see a fence across a road and do not see why it is there, do not take it down until you understand its purpose.

When is it okay to remove the fence?

When you understand why it was built, confirm the original problem no longer applies, and have verified that removing it will not recreate the problem.

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