Remember the Zanzibar Fallacy
Redefining two standards at the same time (I'm certain that they haven't)
The Zanzibar Fallacy
There was once an explorer who came to the tropical island of Zanzibar. Now, it happens that the island of Zanzibar is much longer than it is wide, so that the opposite ends of the island are separated by many miles of hilly jungle country.
This traveller was a naval man by profession, and he had not been long on the island before he was told of a retired naval officer, a countryman of his, who lived at the extreme western end of the island, in a wooden house built high up on the cliffs overlooking the ocean.
The explorer thought that he would like to visit his fellow expatriate, so he journeyed to the man's house, taking but one porter with him, for he preferred to travel light and, anyway, was not an excessively wealthy man. The journey took two days, or maybe it was three, but apart from the expected privations of crossing jungle terrain there was nothing remarkable about his trip. Nothing, that is, except that at noon each day he heard the sound of a naval gun, booming out from beyond the hills to the west and scattering the brightly-coloured tropical birds about his head.
When he reached the ex-officer's house he was made very welcome. All morning they sat together on the veranda overlooking the sea, drank chukka pegs, and talked of home and their lives in the navy. As the time approached midday, the owner asked to be excused. He walked to the far end of the veranda, where there was a quarter-pound cannon, and, consulting his watch, fired a single shot at precisely twelve o'clock. 'I do that every day,' he said to the traveller, who understood perfectly his host's desire to observe naval tradition. 'Tell me,' he asked him. 'How do you ensure that you always fire your gun at exactly midday? Do you take sightings?'
'No need,' he other replied. I kept the ship's chronometer from the old Arethusa and I set my own watch to it every morning.'
'Ah,' said the first. 'But how do you know that the chronometer is correct?'
'That is simple. At the other end of the island there is a clockmaker of great renown who keeps all his timepieces in perfect order. Twice a year I send my chronometer to him and he regulates it for me.'
The traveller spent several enjoyable days at the naval officer's house and they became great friends. 'Give my regards to Mister Jones the clockmaker, won't you?' the old seaman said as they parted. 'I will,' the explorer replied, and they shook hands warmly.
Two weeks later, the traveller reached the far eastern end of Zanzibar and there, in a small town nestling under a ridge of green trees and grey rocks, he found Mr Jones' shop. It was a shop such as you may find anywhere there are clocks and watches to be made or mended – dim and cool, filled with the soft sounds of ticking and chiming. Our explorer introduced himself to the clockmaker and, noticing how well all the watches and clocks in his shop were synchronised, asked him how he made sure that they were all keeping the right time.
'That is simple,' the clockmaker responded. 'At the other end of the island there is a retired naval officer who, every day at twelve o'clock precisely, fires a gun. I set all my clocks by him.'