Fable
The screen on the accountant's desk
The grand accounting office had a long table, with questions, drafts, standard answers, and old accounts all spread out on it. When the new clerk practiced, he could not help glancing at the answers behind him.
The teacher lectured first and forbade peeking. The scribes nodded, but the desks were not separated, and with one glance the future characters and nearby annotations entered their minds. Practice scores were good, but when they actually took up their posts it was chaos.
The second fix was deducting points after the fact. Deductions could make people nervous, but they could not guarantee that every position saw the same materials as during formal operations. The habit of peeking still hid along the edge of the desk.
Later the teacher installed movable screens on the long table. When writing the first line, one could see only the question; by the fifth line, one could see only the first four lines and the permitted ledger pages; when filling a certain cell, one could see only the materials belonging to that cell.
The masking board has further subdivisions. Some blanks are just placeholders and should not participate in judgment; some shopkeeper annotations rank above customer letters; some tool receipts can only be seen by subsequent steps and cannot flow back into earlier decisions.
The accountant did not become duller; instead, he became stable. What each position can see is determined by the structure of the desk, not by the clerk’s self-awareness. The master said that smart people also need boundaries; if their gaze is placed in the wrong spot, the answers they learn will be skewed.
Later, the accounting office took on more complex work: one large account was assigned to multiple people for calculation, some people could only see customer letters, some could only see the manager's instructions, and some results were opened only after the previous step was completed.
The screen was made into a movable arrangement. It was not responsible for calculations, but it determined which papers each position could see and when. The master discovered that many errors were not due to bad arithmetic, but to seeing what should not be seen or failing to see what should be seen. Later, when newcomers started, the senior masters no longer began with abstract terms. Instead, they had them review that failure: where intuition had originally been relied on, why the first fix was insufficient, and how the new arrangement kept risk in a place where it could be checked. Only when they could explain these details clearly, and also point out when to keep using the method and when to upgrade it, were they considered to truly understand it. Later, they also had newcomers practice with this method: first let them do it the old way and see how errors appeared; then redo it under the new rules and see which step was blocked earlier and which step left evidence. If newcomers could only recite names, they would still misuse it in similar situations; only those who could state the applicable boundaries, the costs, and the remedies after failure were allowed to take on work independently.