In this report, we show how, for complex tasks, multi-task learning can improve the accuracy, inference, and maintainability of models.
Learn more.inspired by Jorge Luis Borges
There is a consensus among archaeologists and historians of the Near East that the lost city of Havurtat1 is nothing more than an ancient fabrication; no trace of the city so lavishly described in encyclopedias and maps of antiquity has been found. The numerous excavations around the present-day city of Jolfa on the banks of the Araz–beginning with the English explorer Roger Dimblesby’s expedition in 1878–have failed to unearth so much as an arrowhead. Yet there are still those who hold fast to the truth of the city’s historical existence, owing perhaps to the following account of its abrupt end.
In its eighth-hundred year, a young prince assumed the throne of Havurtat after the occultation2 of his father. The young prince had only recently returned to the city from the frontiers, having rendered his services in the army of the Bronze-age emperor to whom the city pledged fealty. Because of his conscription into the army at an early age, he was unaccustomed to the comforts and plenitude of courtly life in which he found himself at the center, after ascending the seat of power. For the first few years of his reign, the young prince freely indulged in the powers and pleasures of his throne. He threw extravagant banquets, hunted exotic game animals, and commissioned ambitious construction projects, until– as so often happens to princes of happy cities–he grew bored and unhappy, and began contemplating his place in the scheme of things. He withdrew from court and began to spend more and more of his time in the library and in the company of the learned men in his court– seers, poets, judges, and advisers.
One night, standing on the terrace of his palace, looking down at the matrix of squat brick houses of precisely equal dimensions that inhabited square plats of land separated by roads that stretched out to the city’s ramparts, the prince was seized by a despondency he had never experienced before. He asked his guards to fetch his advisers, who, roused from their sleep, were presently brought before the prince, unkempt in their night-time robes.
—How do we rule this city? The prince asked his advisers.
—Justly, replied the advisers in unison.
—What are the instruments of our rule?
—Our laws, prince.
—Who provides these laws?
The advisers were startled by this line of inquiry, especially the oldest among them, who had served not only the prince’s father but also his grandfather; no prince, as far as anyone could remember, had questioned the laws and his own authority. They stuttered over each other for an answer before one stepped forward and spoke.
—Prince, surely you know who wrote our laws–it was the first prince.3 He wrote our laws, which are manifest in the functioning of our city. Our laws are perfectly devised. They have not been broken in eight hundred years.
The prince was not satisfied with his advisers’ answers. He tossed and turned in his bed all night. Just before dawn, he got up and opened the doors to his chamber where two sentries were standing alert, ready to pull their swords–in rather needless caution, as the prince, both for his immortality and the city’s unbreakable laws, faced no threats.
—Take the strongest horse from my stable, the prince whispered to one of the sentries, and ride. Bring me back the vilest and craftiest man you find: a man who cannot abide order, a man who never keeps his word, who has no compunction in stealing, who kills at his whim.
The sentry bowed his head and marched away.
Time passed. Days. Months. The prince carried on as before, disinterestedly sitting at the head of flamboyant banquets, hunting game in the forests past the city’s circular ramparts, anointing new temples with the blood of gazelles and deer–but the sentry and his mission remained often in his thoughts. One year later, the sentry came back to the city. He entered the court deferentially, accompanied by a toothless, hunch-backed old man whose eyes were sunk deep inside his head.
The prince looked at the man and sneered. —This old crow will break our unbreakable laws? He looks like he can’t even break a piece of bread.
—My prince, the sentry replied, I travelled to the edges of the world. I met hundreds of men of unspeakable vice, each surpassing the last in the art of evil. I met men who had sold their own brothers and sisters. But when I met this old man, the crimes of everyone else appeared to be nothing more than childish games. He is three hundred years old, and the reason he stands before us, despite his many transgressions, is because of his ability to outwit every judge and executioner.
The prince leaned forward in his chair. —Old man, do you know that I rule over a perfect city. Our forefathers divined laws for us. The laws are everywhere. Nothing has happened in this city in eight hundred years in violation of the order set by its founders. What more could any sovereign desire? But this does not satisfy me. How can I be sure that I am sovereign when I cannot intervene in this order? How can I exercise my will, if everything happens as it is supposed to?
When he had finished, the old man responded in a soft rasping voice. —All laws can be broken.
—Then show me how.
—Give me a fortnight, your grace.
For two weeks, the old man criss-crossed the city’s streets, talking to its denizens. He avoided his lodgings at the palace, and spent his nights with the seers, learning about the city’s beginnings, the first prince, and its laws. He observed that Havurtans, like all people, had among them deceitful, violent, greedy, and malicious characters. But the laws of the city, he understood, had created ideal conditions, where an optimal distribution of resources, pre-emptive action against malicious actors, and transparency had not only disincentivized law-breaking but allowed the authorities to stop potential law-breakers before they broke the law.
He also learned that the eternal source of these laws was the prince, before whose anxious eyes, the old man stood once again two weeks later. —Your grace, the old man said, what is said about your city is true. The authors of your city’s laws foresaw and understood every event and occurrence in this city, even down, it seems, to the very movement of leaves. The laws they wrote indeed cannot be broken. However, there’s one event they failed to pre-empt; there is one law that can be broken.
—Well, what are you waiting for? Tell me! The prince exclaimed.
—Regicide.
Saying this, the old man quietly stepped back. The prince had his answer. Slowly, he stood up from his chair and descended from the dais. He gestured at the sentry, who fearfully approached, his hand clutching the hilt of his sword; the prince tapped the sentry’s hand gently, and ordered him to strike.