Most Rules Exist for a Reason
A 500-record limit once saved us from a cascading bug. Worked perfectly for years. Then a new team member asked why it existed. Nobody remembered. Got removed. Three months later, the original condition recurred.
Working guardrails become invisible. Once they prevent the problem reliably, people forget why they exist. Then they remove them. This is Chesterton’s fence: don’t remove a fence until you understand why it was built.
Note that this doesn’t mean never remove a fence, it means think about why the fence was built before removing it. Rules, laws, CI/CD tests, etc. are lossy encodings of intent — a reflection of what someone meant, applied to the state of things at the time.
“Thou shalt not desire thy neighbour’s house” technically says nothing about thy neighbour’s car, nor their lunch in the office fridge. But that probably shouldn’t give you free rein to nick either one.
Why was the fence built? Does the situation still apply? Do we have better ways of solving it?
The same applies to AI agents. An agent encountering a constraint it doesn’t understand will do what any capable new hire would: question it. The difference is that a new hire usually asks before acting. An agent, unless you’ve built that pause into the process, might just remove the fence and keep going.
We built that switch into our own tools. It’s called --force. Failing tests? --skip. Permission error? --force. Agents reach for it first because it’s the path of least resistance — which is exactly what we trained them to find. But humans lean toward it too, unless they believe there are consequences. One large company added a required “reason” field for force-merges. The biggest build breaks still came with REASON="I know what I'm doing." Perhaps they did, but they still broke 50% of all Google’s builds.
Chesterton’s fence is not a monument. It is a question.
“If you put a large switch in a cave with a sign saying ‘End-of-the-World Switch. PLEASE DO NOT TOUCH,’ the paint wouldn’t even have time to dry.” — Terry Pratchett
Related reading:
- I have No Memory Of This Place — on what happens when the “why” behind the fence disappears entirely, and what you owe the next person
- Oops I Did It Again, I Forgot –dry-run — on building fences that ask questions before they let you through
- Death by a Thousand Tests — on which rules earn their keep, and at what cost