Fable
Three accounting paths calculate the same number
At the salt warehouse's year-end inventory, young accountants often used the fastest algorithm. Most of the time it was right, but when discounts, spoilage and delayed payments were mixed together, it easily went wrong.
The warehouse keeper first had him memorize the algorithm. The more thoroughly he memorized it, the more convincing the errors looked; once the beginning went off track, every subsequent step seemed perfectly logical, and even bystanders found it hard to notice.
The old accountant did not immediately point out the answer. He had the three apprentices calculate from different angles: one by truck, one by warehouse slot, one by receipt. Each wrote down their own intermediate process.
The first time, the three results were all different. The old accountant had them check the discrepancy and found that one receipt had been counted twice. The second time, two results matched and one was high; the high path was found to have missed deducting a loss.
The warehouse owner asked why not simply trust the most senior person. The old accountant said that in complex accounts, one path may look very confident; if multiple independent paths land on the same answer, the credibility is higher.
They also did not vote blindly. If all three routes used the same erroneous draft, more votes would be useless. So each accounting route had to start from different clues as much as possible, and when necessary people had to be changed to recalculate.
Later, the salt warehouse applied this method to the largest accounts most prone to error. Simple small accounts were still calculated directly, because recalculating them several times was not worth it; only truly troublesome accounts needed several paths to support one another.
When the accounting was finished, the warehouse owner saw several different lines of provenance beside the final number. The answer was accepted not because it was loud, but because multiple methods supported one another and disagreements were traced to a place where they could be explained. The old accountant also set a rule for apprentices: different routes must first be completed independently, then compared. If they consulted one another from the start, the three routes might look consistent while actually going astray together. Disagreement is not trouble; it is the place where errors are found. Later, the salt warehouse divided even consistent answers into two types: those that independently arrived at the same point were trustworthy; those copied from one another were dangerous. Surface sameness is not enough; the provenance must also be clean. Later, during review, everyone wrote this lesson into daily rules: first look at where on site the result was truly changed, then decide what to keep, repair, or restrict. If you look only at surface excitement, you will fall in the same place next time.