Fable
The night watchman only watches the seven streets around him
The night patrol bureau of the great city used to require every night watchman to keep track of all movements across the city at all times. When the city was small, this was still possible, but after the city grew larger, everyone was dragged down by distant news, and no one handled nearby fires first.
The minister first added more messengers, to deliver news across the city to everyone faster. There was more news, but judgment grew slower, and the night watchmen read bulletins every day. The second fix was to keep only the master summary. A summary reduces the load, but it often misses small changes that just happened nearby—and those changes are the most likely to affect the next action.
One night, a warehouse three miles outside the west city caught fire. The nearby night watchman was still reading a long report about a caravan dispute at the east gate, and by the time he noticed the smell of smoke, the fire had already burned through two rooms. Later, the director changed the patrol rules: each night watchman mainly watched the seven streets around himself, and as the team advanced, the window slid forward as well.
This does not mean never looking into the distance. Important remote messages can be conveyed through special bells, summaries, or high-tower flags, but daily attention is given first to the local context.
The new rules kept the cost of patrolling the Great Wall manageable. The amount of information each person handled stayed stable and did not expand endlessly as the city grew longer, and nearby changes were no longer drowned out by distant messages.
The director at one point required the night watchmen to memorize all notices. But when a tavern quarrel in the north city reached the south gate, the south gate already had an oil-pot fire; when dog barking in the western suburbs was written into the ledger, no one smelled the real smoke in the eastern ward. The more complete the citywide information became, the slower the response on the ground.
The old night watchman changed his method: each person focused on the three streets in front of and behind him, passing short whistles at the boundaries, and only matters such as a major fire, flood, or thieves entering the city were spread throughout the city. The night watchmen no longer pretended to see all places at once, but instead slid their limited gaze forward, seeing nearby places clearly and leaving only necessary reminders for distant ones. Later the office still kept the citywide register, but that was for after-the-fact review, no longer pressed onto every night watchman's shoulders. At night, firefighting relied on nearby judgment, while long-term tracking relied on a window sliding all the way through; the two ways of seeing each had their place.
The director said in the end, a long road does not mean seeing the whole city at every step. First steadily watch what is near you, then design a few bridges to distant places—that is scalable order.