Chesterton's Fence

1. The gate across the road

Chesterton put it in 1929, in the essay “The Drift from Domesticity” in The Thing. It was read tonight in the 1946 edition, scanned by the Digital Library of India, page 29:

There exists in such a case a certain institution or law; let us say, for the sake of simplicity, a fence or gate erected across a road. The more modern type of reformer goes gaily up to it and says, “I don’t see the use of this; let us clear it away.” To which the more intelligent type of reformer will do well to answer: “If you don’t see the use of it, I certainly won’t let you clear it away. Go away and think.”

His reason is that the gate or fence did not grow there. Somebody put it up for a reason. Here the frame stops fitting, and the place where it stops is the finding.

This fence did grow there.

2. The walk to the store

On 30 September the Seafarer spent 61.5% of the day, 14,767 of 24,000 steps, on one task: making a set of stone tools. On the 29th it was 43%. The task began again every 2.9 sim-seconds. Neither day holds a single line saying he made a set. The count comes from tools/why.mjs, which replays the day as it aired and names the rule behind every step.

Two pieces of the engine disagreed about what he wanted. The rule that chooses his work (ownChoice, sim.ts:6541) called a set with six uses or fewer spent and sent him to remake it in stone. The code that finishes the job (finishCraft, sim.ts:11798) asks toolsWanted (sim.ts:5820). That function wants the same tier again only once a set is broken. Until then it wants the next tier up, iron. There is no iron in the valley. So the finish found nothing to make and returned without a word, and the rule sent him back.

Nobody wrote the walk. It was the space between two rules.

3. Clearing it away

You said “Go on that”, and the first fix was the obvious one: let the finish make what the rule asked for, a new stone set. The Seafarer would make one and stop walking. A check written for the purpose passed.

Then the whole gate ran, and check:output went red. It builds a valley of its own, gives it every workshop, runs it for 12,000 ticks and asks whether each kind of bench was ever worked. Measured tonight in that valley, on the old engine and on the first fix:

Remade early, a stone set came back with about fifty uses. A settler holding it was no longer spent, so the rule stopped reaching for iron. Under the old engine the same settler had walked to the store until iron could be paid for, and then the finish made iron. The walk had been a queue for iron. Clearing it away let the queue go home, and the mill went quiet.

4. Coming back to say what it was for

The fix that landed asks the finishing code’s question before sending anybody: the rule sends a settler to make tools only when toolsWanted says the craft will make something (sim.ts:6560). A settler with a worn stone set and no iron in reach now works the set down and remakes it when it breaks. When iron can be paid for, he makes iron.

The check for it, check:toolmaker, starts from the aired opening with the Seafarer’s own worn set. On the old engine he takes 82 craft tasks in 6,000 steps and makes nothing. On the fix he takes two, and makes one set. Replayed under the fix, the 30th’s share on that task falls from 61.5% to 0.6%. The valley in check:output keeps its 20 iron sets and both mills work.

The walk is gone. Now it has been told what it was for.