The other side of Chesterton's Fence

In 1929 G. K. Chesterton described a fence across a road. One reformer walks up to it and says he sees no use for it, so clear it away. A second reformer answers: if you do not see the use of it, I will not let you clear it away. Go away and think. When you can come back and tell me what it is for, I may allow you to destroy it.

People teach that as Chesterton's Fence, and they usually teach it as a lesson about respect for the past. It is that. It is also a lesson about order, and the order is the one Gap Last runs.

The fence is a bound

The first reformer has already named a cause. Some fool put this here. He has not named the gap, which is: I do not know why this is here. He is building a mechanism on a what he has not framed. Chesterton's answer is the prohibition. Do not act on the cause until you can name the gap. Go find out who built it, when, against what, at what cost. Then decide.

That is Gap Last applied to an artifact instead of an event. The fence is the bound. "Some fool" is the first noun. The gap is why it stands.

What a fence is made of

A fence is a cause made physical. Somebody paid for it, and the payment was usually in the currency that makes people build fences: a child in the road, a flood, a failed season, a lawsuit, a death nobody wants repeated. The fence encodes the question those people answered and how sure they were. Their pain is a trace. When the first reformer tears the fence down unread, he throws away the trace, and the payment with it.

That is the same waste Gap Last exists to prevent, run the other direction along time. A thin cause aims the next warning system at the wrong object. A fence removed unread throws away the last warning those people paid for.

The other side

Chesterton stands on one side of the fence, facing the past. He protects the builders' what from the present's thin how: it is useless, remove it.

Gap Last stands on the other side, facing forward. It protects the future's fence from the present's thin what. When it is your turn to build, someone will walk up to your fence in twenty years and, rightly, refuse to remove it without understanding it. If you built it on a first noun, you have handed them a fence that bounds nothing real and a duty to respect it anyway. They will be as exposed as before, with the added harm of believing the fence is doing something.

So the two ideas are one instruction seen from both ends. Chesterton: find the gap the fence closed before you take it down. Gap Last: name the gap before you put one up.

Where they rub

People abuse Chesterton's Fence. They use it as a veto for every accepted cause: the established explanation is the fence, do not touch it. Chesterton never said that. He said go and think, then come back, and then I may allow you to destroy it. The burden is understanding, not preservation.

Gap Last says when that permission applies. When better evidence arrives, the question moves, and a fence built for the old question can be retired. That is not a failure and it is not disrespect to the people who built it. They answered the question they had, with the evidence they had. On Langtang Lirung, Wednesday's label, glacier collapse, was honest work with Wednesday's images. Thursday moved the question to rock. Nobody had to be a fool for the label to need moving.

The plaque

The reconstruction log, the last of the nine sections in the Gap Last method, is what every fence should have carried: a plaque saying which gap this closed, how sure the builders were, and what evidence would change it. Chesterton's second reformer would not have had to send anyone away to think. He could have read it.

Gap Last owes Chesterton that much, and pays it gladly. He asks what gap the fence closed before you remove it. The Gap Last method asks you to name the gap before you build one. Both refuse the same move: a cause invented ahead of the question.