Don't remove a fence until you understand why it was put there.
Chesterton's 1929 formulation: the reformer who cannot say why the fence is there is not yet qualified to remove it. It is an argument about the burden of inquiry, not a prohibition on removal.
In practice
- A new head of operations removes the two-signature rule on refunds and discovers in month four why it was introduced in the first place.
- A team deletes a scheduled job nobody could explain, and the month-end reconciliation fails for the first time in six years.