What do rubber tyres have to do with delicious food? The answer lies in the story of the Michelin brothers. French inventors Edouard and Andre Michelin created the Michelin tyre company in 1889 and transformed the travel industry. A few decades later, they began publishing a guide to highlight food in restaurants worth travelling for, which, of course, they'd need strong Michelin tyres to reach. Nowadays, the coveted Michelin star – an award given to only the world's finest restaurants – is one of the culinary world's highest accolades. But the rating system is somewhat shrouded in mystery.

橡胶轮胎与美味食物有什么关系？ 答案在于米其林兄弟的故事。 法国发明家爱德华（Edouard）和安德烈·米歇林（Andre Michelin）于1889年成立了米其林轮胎公司，并改变了旅游业。 几十年后，他们开始发布一份指南，以突出值得旅行的餐馆中的食物，当然，他们需要强大的米其林轮胎才能到达。 如今，令人垂涎的米其林之星（仅授予世界上最好的餐厅）是烹饪界最高的荣誉之一。 但是评级系统在某种程度上笼罩在神秘之中。

The Michelin Guide itself says their inspectors take into account five criteria: the quality of the ingredients, the harmony of flavours, the mastery of techniques, the personality of the chef as expressed through their cuisine and consistency both across the entire menu and over time. But the inspectors are anonymous, and chefs are always kept in the dark about when they are going to visit. "We're never aware of the inspectors' visit," said Julia Sedefdjian, who became France's youngest Michelin-starred chef at the age of 21. "If they introduce themselves, it's only after they've eaten. And often – very often – they never introduce themselves at all."

《米其林指南》本身说，他们的检查员考虑了五个标准：成分的质量，口味的和谐，掌握技术的掌握，厨师的个性，通过其美食和整个菜单上的菜单和一致性表达。 但是检查员是匿名的，厨师何时要访问厨师。 朱莉娅·塞夫迪安（Julia Sedefdjian）说：“我们从来没有意识到检查员的访问，他在21岁时成为法国最年轻的米其林星级厨师。“如果他们自我介绍，只有在他们吃饭之后，他们就经常 - 经常 - 通常 - 他们从不介绍自己。”

And how much does the overall ambience of a restaurant play into the ratings? Ideas vary. Chef Maxime Bouttier, who has worked in Michelin-starred restaurants across France for 15 years, thinks details like white tablecloths and background piano music can help to tick boxes for inspectors. Despite this, Bouttier's own restaurant doesn't have tablecloths, and his clientele listen to '80s rap while dining, yet his restaurant earnt a star less than a year after opening. The Michelin Guide says a Michelin star is awarded for the food on the plate, nothing else, and that the style and degree of formality have no bearing on the award whatsoever.

餐厅的整体氛围有多少？ 想法各不相同。 厨师Maxime Bouttier曾在法国各地的米其林星级餐厅工作了15年，他认为诸如白色桌布和背景钢琴音乐之类的细节可以帮助检查员打勾检查员。 尽管如此，Bouttier自己的餐厅没有桌布，他的客户在用餐时听着80年代的说唱，但他的餐厅在开业后不到一年就赚了一颗明星。 《米其林指南》说，米其林明星因盘子上的食物而被授予，别无其他，形式的风格和程度与该奖项无关。

Michelin stars can make or break a chef's culinary career. Earning one gives a chef more recognition, more table bookings and can allow them to raise their prices. But there's also the risk of losing one, and with that comes a lot of pressure. 

位米其林明星可以使厨师的烹饪生涯创造或破坏。 赚取的人会给厨师提供更多的认可，更多的餐桌预订，并可以使他们提高价格。 但是，也有失去一个的风险，随之而来的是很大的压力。 

Kew's Palm House is a wonder of the Victorian age. When it opened in 1848, it was the largest glass house ever constructed. But the hot and humid conditions inside that are essential for the tropical plants it houses have taken their toll on the building. Its ornate painted metalwork is rusting, and 16,000 panes of glass need to be replaced.

邱园的棕榈温室是维多利亚时代的奇观。在 1848 年开放时，它曾是当时人类建造过的最大的玻璃温室。然而，它内部的高温潮湿环境对于它所收容的热带植物来说是必需的，不过这也让建筑本身受到了损害。棕榈温室装饰华丽的、涂有颜料的金属部件开始生锈，1 万 6 千块玻璃窗板也需要被更换。

The renovation will begin in two years' time. But the horticulturalists at Kew have already started to relocate some of the precious plants as more than 1,000 species need to be removed and safely stored before work can start. Kew is also taking the opportunity to make the greenhouse much greener, replacing the gas boilers with huge heat pumps to drastically cut its emissions.

翻新工程将在两年后开始。但邱园的园艺师们已经开始着手迁移部分珍贵的植物，因为有超过 1000 种植物品种需要在施工前被移出并妥善保存。邱园还将借此机会让温室变得更加环保，用大型热泵替代燃气锅炉，以大幅减少污染物排放量。

Use of technology in sports is supposed to be able to provide accurate and instant feedback, with better decision-making and reduced errors compared to human intervention. But is that always the case?1在体育中使用技术应该能够提供准确，即时的反馈，与人干预相比，决策更好，并且错误减少。 但是总是这样吗？

The annual tennis tournament Wimbledon made the decision this year to replace their line judges. These have traditionally been men and women who judge whether the ball is in or out of bounds, but they were switched out for AI that analyses camera footage, which should be faster and more accurate. Despite this, the electronic line calling system failed just a week into the 2025 championship. The ball-tracking technology was turned off by a person accidentally. This meant a point had to be replayed, which resulted in Sonay Kartal controversially winning the game. If technology needs humans to operate it in the first place, whose fault is it in situations like these where things go wrong?年度网球锦标赛温布尔登今年决定取代他们的阵容法官。 传统上，这些是男人和女人，他们判断球是界限还是超出范围，但是他们被转移到了分析摄像机镜头的AI上，这应该更快，更准确。 尽管如此，在2025年锦标赛中，电子线路通话系统还是失败了一周。 偶然的人关闭了球跟踪技术。 这意味着必须重播一个观点，这导致Sonay Kartal有争议地赢得了比赛。 如果技术首先需要人类来操作它，那么在这种情况下出现问题的情况下是谁的错？

In football, referees often come under fire for their decision-making. But VAR, that's 'video assistant referee', is regularly used in football these days too. A referee can ask for a VAR check, which means that if they are unsure of something, like the awarding of a penalty, they can double-check their own judgement. However, last football season, VAR made oversights which angered a lot of managers, players and fans. They said the system was notfit for purpose and even favoured some teams over others. Despite this, the Premier League's chief football officer, Tony Scholes, said during the middle of last year's season that standards were actually higher than ever. "Before VAR, 82% of the decisions made were deemed to be correct. In the season so far, that figure is 96%," he said.在足球比赛中，裁判经常因决策而受到抨击。 但是，这是“视频助理裁判”，如今也经常在足球中使用。 裁判可以要求进行VAR检查，这意味着，如果他们不确定某件事，例如判处罚款，他们可以仔细检查自己的判断。 但是，上一个足球赛季，VAR进行了监督，激怒了许多经理，球员和球迷。 他们说，该系统不适合目的，甚至偏爱其他团队而不是其他团队。 尽管如此，英超联赛的首席足球官托尼·斯科尔斯（Tony Scholes）表示，在去年中期，标准实际上比以往任何时候都要高。 他说：“在VAR之前，做出的决定中有82％被认为是正确的。到目前为止，这个数字为96％。”

So,why do we still not trust technology if it often improves a situation? Professor Gina Neff from Cambridge University says that we have a very strong, in-built sense of fairness." The machine makes decisions based on the set of rules it's been programmed to adjudicate," she said. "Right now, in many areas where AI is touching our lives, we feel like humans understand the context much better than the machine."那么，如果技术经常改善情况，为什么我们仍然不信任技术？ 剑桥大学的吉娜·内夫（Gina Neff）教授说，我们有一种非常强烈的内在公平意识。“该机器根据一套规则做出了决定，它已被编程以裁定，”她说。 “目前，在AI触及我们生活的许多领域，我们觉得人类比机器更好地了解环境。

”Whether you trust it or not, technology is here to stay, including in the world of sport.无论您是否信任，技术都将留在这里，包括运动世界。

The logic of common knowledge and social relationships explains why we all deplore the hypocrisy and white lies and role playing of everyday social interaction, but we wouldn't want to live without them.公共知识与社会关系的逻辑，解释了为什么我们一方面都厌恶日常社交中的虚伪、小谎言以及角色扮演，但另一方面又不愿意没有它们的生活。

As dystopian comedies like "Liar Liar" play out.就像反乌托邦式喜剧《大话王》（Liar Liar）所展现的那样。

Our relationships are underpinned by a common understanding of limitless loyalty and generosity.我们的关系是建立在一种“无限忠诚与慷慨”的共同理解之上的。

Privately, we know they're fictions, but making these rude realities common knowledge would pollute the pool of common assumptions that allow us to get along.私下里，我们都知道这些是虚构的，但如果把这些残酷的现实变成公共知识，就会污染那一池让我们得以相处的共同假设。

We also have to get along in less intimate relationships, and in those cases, we rely on norms: ways of living together that aren’t written down by lawgivers or enforced by the police, but exist because everyone knows they exist.我们还需要在不那么亲密的关系中相处，在这些情况下，我们依赖于“规范”——它们不是立法者写下的，也不是由警察强制执行的，而是因为每个人都知道它们存在，所以它们才存在。

In social life, basic civility depends on norms such as that you don't brazenly lie, you don't insult people to their faces, you don't prosecute personal vendettas.在社会生活中，基本的礼貌依赖于一些规范，比如：你不能厚颜无耻地撒谎、不能当面侮辱他人、不能公报私仇。

In the anarchic global arena, peace depends on norms such as that nation states are immortal, national borders are grandfathered in, conquest is unacceptable, and nuclear weapons are unthinkable.在无政府状态的全球舞台上，和平依赖于一些规范，比如：国家是永久存在的、国界是既定且不可轻易更改的、征服行为是不可接受的、使用核武器是不可想象的。

These norms arepropped upby nothing but common acceptance, and so they're vulnerable to imploding if they are overtly flouted, or even if there is loose talk about flouting them.这些规范仅仅依靠“普遍接受”来支撑，因此一旦被公然违背，甚至只是被随意谈论要违背，它们就有可能瞬间崩塌。

I hope that, having explained the logic behind human harmony, I don't have to explain how these norms are currently under threat or what is at stake if we lose them.我希望，在解释了人类和谐背后的逻辑之后，我就不必再解释这些规范目前是如何受到威胁，以及如果失去它们会付出怎样的代价。

As a man once said, "What's there to say? It's so obvious."正如有人曾经说过的：“这还有什么好说的？太明显了。”

Or laughter, where an unignorable noise can expose the common assumptions among everyone who gets the joke.或者是笑声，那种无法忽视的声音能够揭示所有明白这个笑话的人之间的共同假设。

Conversely, when we worry about upending a relationship, we might go to great lengths to repress common knowledge. We might avoid looking someone in the eye, or pretend to ignore the elephant in the room or mumble with great incoherence.相反，当我们担心会颠覆一段关系时，可能会竭尽全力压制“公共知识”。我们可能会避免直视对方的眼睛，假装忽视房间里的“大象”，或者用极其含糊的方式咕哝说话。

This is why, in everyday conversation, we often don't blurt out what we mean in so many words, but veil our intentions in innuendo and euphemism, counting on our listeners to catch ourdrift.这就是为什么在日常对话中，我们常常不会直截了当地说出自己的意思，而是用暗示和委婉语来掩饰自己的意图，并依赖听众去心领神会。

A classic example is the sexual come on "Would you like to come up and see my etchings," which by the 1930s was so familiar that James Thurber could draw a cartoon in which the hapless man says to his date, "You wait here and I'll bring the etchings down."一个经典的例子是性暗示“你想上楼看看我的蚀刻画吗”，到了20世纪30年代已经如此普及，以至于詹姆斯·瑟伯能画出这样一幅漫画：倒霉的男士对他的约会对象说，“你在这等着，我把蚀刻画拿下来给你看。”

A century later, etchings has become “Netflix and chill.”一个世纪后，“蚀刻画”已经变成了“Netflix and chill”（看网飞电影并发生亲密关系的委婉说法）。

We also veil our bribes, as in, "Gee, officer, is there some way we might settle the ticket here?"我们也会掩饰我们的贿赂，比如说：“哎呀，警官，有没有办法我们可以在这里把罚单的事解决掉？”

And our threats, as in, "I'm so delighted to learn that you're on the jury of the Soprano trial. It's an important civic duty that we should all take part in. You've got a wife and kids, we know you'll do the right thing."同样，我们也会掩饰我们的威胁，比如说：“我很高兴得知你是‘索普拉诺’审判的陪审员。这是一项我们都应该参与的重要公民义务。你有妻子和孩子，我们相信你会做正确的事。”

The point of innuendo is not plausible deniability because these euphemisms don't pass the giggle test, but rather deniability of common knowledge.暗示的目的并不是为了让自己“貌似有否认的可能”，因为这些委婉语经不起一笑置之的检验，而是为了否认“公共知识”的成立。

If Harry says to Sally, "Want to come up for Netflix and chill," and Sally turns him down, well, Sally knows she's turned down a sexual overture, and Harry knows that Sally has turned down a sexual overture.如果哈利对莎莉说：“要不要上楼Netflix and chill？”而莎莉拒绝了，那么莎莉知道自己拒绝了一个性暗示，哈利也知道莎莉拒绝了一个性暗示。

But does Sally know that Harry knows? She could think, "Maybe he thinks I'm naive."但是莎莉知道哈利知道吗？她可能会想：“也许他觉得我很天真。”

And does Harry know that Sally knows that Harry knows? He could think, "Maybe she thinks I'm dense."而哈利知道莎莉知道哈利知道吗？他可能会想：“也许她觉得我很迟钝。”

Without the common knowledge, they can maintain the fiction of a platonic relationship.没有公共知识，他们就能维持一种“柏拉图式关系”的假象。

But if Harry were to have said, “Want to come up and have sex,” and Sally said no, well, now Harry knows that Sally knows that Harry knows that Sally knows.但是，如果哈利说的是：“要不要上楼做爱？”而莎莉拒绝了，那么此时哈利知道莎莉知道哈利知道莎莉知道。

With this common knowledge, they can no longer maintain the fiction of a platonic friendship.有了这样的公共知识，他们就再也无法维持柏拉图式友谊的假象了。

And that's what lies behind the intuition that with bare-faced speech, you can't take it back. It's out there.这正是那种直觉背后的原因：一旦赤裸裸地说出来，就无法收回——它已经在那里了。

This can set off cycles of exuberant recursive mentalizing, as investors desperately search for focal points, each one buying an investment not because of its inherent productive value but because they hope to unload it at a profit on future investors, greater fools.这会引发一种亢奋的递归心理博弈循环——投资者拼命寻找“焦点”，他们买入一种投资并不是因为它本身具有生产价值，而是希望将它高价转手卖给未来的投资者，也就是所谓的“更大的傻瓜”。

This can set everyone off in search of conspicuous focal points such as Super Bowl ads. Everyone knows that everyone watches the Super Bowl. In 2022, cryptocurrency exchanges ran high-concept ads in which they tried to gin up a common expectation of rising prices not by touting any of the advantages of cryptocurrency but by warning, "Don't be like Larry. Don't miss out."这会让所有人去寻找显眼的焦点，比如“超级碗”的广告。人人都知道人人会看超级碗。2022年，加密货币交易所投放了创意十足的广告，他们试图制造一种价格上涨的共同预期，不是通过宣传加密货币的优势，而是通过警告人们——“别像拉里那样错过机会。”

Now, of course, it's only so long that an asset can levitate in midair, suspended by nothing but common expectation. Bubbles pop when the market runs out of greater fools who don’t want to miss out on the next best thing or when the doubt itself becomes common knowledge.当然，一项资产只靠共同预期“悬在空中”的时间有限。当市场上再也没有愿意接盘、不想错过下一个机会的“更大的傻瓜”，或者当怀疑本身变成了公共知识时，泡沫就会破裂。

This can send investors running for the exits, each desperate to sell a security out of fear that everyone else is desperate to sell it. The result can be a bank run or hyperinflation or a Great Depression.这会导致投资者争相出逃——每个人都急着卖掉手中的证券，因为害怕其他人也急着卖。结果可能就是银行挤兑、恶性通货膨胀，甚至是大萧条。

When Franklin Delano Roosevelt said, "The only thing we have to fear is fear itself," it was not a feel-good bromide, but a theorem of common knowledge.当富兰克林·德拉诺·罗斯福说“我们唯一需要害怕的就是恐惧本身”时，这并不是一句鼓舞人心的鸡汤，而是“公共知识”定理的体现。

With investors constantly on the lookout for focal points, financial leaders have to be wordsmiths, mystics and occasionally, comedians. Alan Greenspan once said, "Since I've become a central banker, I've learned to mumble with great incoherence."在投资者不断寻找“焦点”的环境下，金融领袖必须既是语言大师，又是神秘主义者，有时甚至是喜剧演员。艾伦·格林斯潘曾说：“自从我成了央行行长，我就学会了用极度含糊的方式咕哝说话。”

"If I seem unduly clear to you, you must have misunderstood what I said."“如果我看起来说得过于清楚，那你一定是误解了我的意思。”

After Jimmy Carter told his inflation czar, Alfred Kahn, never to use the self-fulfilling word "depression," he said, "OK, but we're in danger of having the biggest banana in 45 years."当吉米·卡特告诉他的通胀主管阿尔弗雷德·卡恩，绝不能使用那个会自我应验的词——“经济萧条”——时，卡恩说：“好吧，但我们正面临45年来最大的香蕉危机。”

My own interest in common knowledge comes from its role in social relationships. A relationship is a coordination game. Two people are friends or lovers or allies, or dominant and subordinate or transaction partners because each one knows the other one knows that they are.我个人对“公共知识”的兴趣，源于它在社会关系中的作用。一段关系本质上是一场协调游戏。两个人之所以是朋友、恋人、盟友，或者是上下级、交易伙伴，是因为他们彼此知道对方知道他们的关系。

And this common knowledge can be cemented by a number of common knowledge generating signals. Like eye contact, where you're looking at the part of the person that's looking at the part of you that's looking at that part of them. Or blushing, where you feel the heat of the cheeks, reddening of your cheeks from the inside, knowing that other people can see it from the outside.这种“公共知识”可以通过多种能生成公共知识的信号来巩固。例如，眼神接触——你在看对方看着你的那个部位；又或者是脸红——你从内部感受到脸颊发热变红，同时知道别人从外部能看到这一点。

At larger scales, common salience or focal points and conventions, drive a lot of our legal and financial coordination. An everyday example is driving on the left, or on the right. It doesn't matter as long as everyone agrees to drive on the same side, as in the joke about the woman who calls her husband during his morning commute and says, "Be careful, honey. The radio says that there's a maniac driving on the wrong side of the freeway."在更大的范围内，共同的显著性（焦点）和约定，驱动了我们大量的法律与金融协作。一个日常例子是——在左侧行驶还是在右侧行驶。只要大家一致，选哪一边都无所谓。这就像那个笑话：一位女士在丈夫的早高峰通勤途中打电话对他说：“小心点，亲爱的，广播里说高速公路上有个疯子在逆行。”

And he says, "One maniac? There are hundreds of them."丈夫回答：“一个疯子？有几百个呢。”

Another everyday example is money. I accept a piece of paper in exchange for an old chair, because I know that my grocer will accept it in exchange for some groceries because he knows his supplier will accept it, and so on.另一个日常例子是货币。我愿意用一张纸来交换一把旧椅子，因为我知道杂货商会接受它换取食品，而他也知道他的供货商会接受它，如此循环。

Now not all the examples are this obvious. Why are autocrats terrified of public protests? Well the basic reason was explained by Gandhi in the eponymous movie when he said, "100,000 Englishmen cannot control 350 million Indians if the Indians refuse to cooperate." The problem is that the Indians can't refuse to cooperate if each one fears that no one will join him.当然，并非所有例子都这么显而易见。为什么独裁者会害怕公众示威？根本原因在《甘地》这部电影中就有解释——甘地说：“如果印度人拒绝合作，十万英国人无法统治三亿五千万印度人。”问题在于，如果每个印度人都担心没有人会和自己一起行动，他们就不可能拒绝合作。

In a public demonstration, each protester can see the other protesters see the other protesters, and this common knowledge allows them to coordinate their resistance, whether by literally storming the palace or by bringing the apparatus of the state to a halt through boycotts and work stoppages.在一次公开示威中，每个抗议者都能看到其他抗议者看到其他抗议者的存在，这种“公共知识”让他们得以协调抵抗——无论是直接冲击王宫，还是通过抵制与罢工让国家机器停摆。

This is the basis for a joke from the old Soviet Union, in which a man in Red Square is handing out leaflets to passersby. Soon enough, the KGB arrest him, only to discover that the leaflets are blanksheetsof paper. They say, "What is the meaning of this?"这就是一个来自前苏联笑话的逻辑基础：一个人在红场向路人发传单，很快就被克格勃逮捕。但当他们查看传单时，发现全是白纸。他们问：“这是什么意思？”

And the man says, "What's there to say? It's so obvious."那人答道：“还用说吗？这不是显而易见吗？”
The point of the joke is the man was generating subversive common knowledge. And in a case of life imitating a joke, in recent years, Russian police have arrested several people for holding, yes, blank signs.这个笑话的重点是——那个人在制造颠覆性的“公共知识”。而在现实生活模仿笑话的案例中，近年来俄罗斯警方确实逮捕了几名举着……对，空白标语牌的人。

Another non-obvious example comes from the world of investing. John Maynard Keynes compared speculative investing to a newspaper beauty contest, in which the winner is not the woman with the prettiest face but the contestant who chooses the face that is chosen by the greatest number of other contestants, each of whom is anticipating the choices of other contestants, and so on.另一个不那么显而易见的例子来自投资领域。约翰·梅纳德·凯恩斯将投机投资比作报纸上的选美比赛，比赛的赢家并不是选出最美面孔的人，而是选出最多其他参赛者会选的面孔的人——而每个参赛者都在推测其他参赛者的选择，如此往复。

When the little boy said the emperor was naked, he wasn't telling them anything they didn't already know. But he added to their knowledge nonetheless. By blurting out what everyone could see within earshot of the others, he ensured that everyone knew that everyone else knew what they knew, that everyone knew that, and so on. And that changed their relationship with the emperor from obsequious deference to ridicule and scorn.当那个小男孩说皇帝没穿衣服时，他并没有告诉大家他们原本不知道的事情。但他仍然在一定程度上增加了他们的认知。因为他当众喊出大家都能看到的事实，让所有人都知道了其他人也知道他们所知道的，而所有人也知道这一点，如此循环往复。于是，这改变了他们对皇帝的态度——从谄媚恭敬转为嘲笑与蔑视。

Hans Christian Andersen's immortal story draws on a momentous logical distinction. With private knowledge, I know something, and you know it. With common knowledge, I know that fact, and you know it, but in addition, I know that you know it, and you know that I know it, and I know that you know that I know it, ad infinitum. Of course, the reason that common knowledge is significant is that it is essential for coordination.安徒生这篇不朽的故事揭示了一个重要的逻辑区别：在“私有知识”中，我知道某件事，你也知道它。而在“公共知识”中，我知道这个事实，你也知道，但除此之外，我知道你知道它，你也知道我知道它，我还知道你知道我知道它，如此无限递归。当然，“公共知识”之所以重要，是因为它对于协调行动至关重要。

In a classic example from Thomas Schelling, a couple is separated in Manhattan, incommunicado, and somehow must find each other. Well he knows that she likes to browse the aisles of certain bookstore, so he heads there. But then he realizes that she knows that he likes to hang out in a certain camera store, so he changes course until he figures that she will anticipate that he will guess that she will opt for the bookstore. So he does another about face, only for it to dawn on him that it will occur to her that he knows that she is aware that he likes to haunt the bookstore, so he pirouettes once again. Meanwhile, she is whipsawed by the same futile empathy. Nothing short of common knowledge can guarantee that they'll end up at the same place and at the same time.托马斯·谢林的一个经典例子是：一对情侣在曼哈顿走散，无法联系，但必须想办法找到对方。男方知道女方喜欢逛某家书店，于是往那边走；但他又想到，女方知道他喜欢待在某家相机店，于是改道过去；接着他又推测，女方可能会预料到他会猜她会选择书店，于是他再次掉头；然而他又意识到，女方可能会想到他知道她清楚他喜欢去书店，于是他又转回去。与此同时，女方也在被同样无休止的推测折腾着。除了“公共知识”，没有任何东西能确保他们在同一时间出现在同一地点。

Of course, no one can think an infinite Russian doll of “I know that she knows that I know that she knows” thoughts. Our heads start to spin with three or four layers, let alone an infinite number.当然，没有人能在脑中无限套娃地思考“我知道她知道我知道她知道”这种想法。三四层就足以让人头晕，更别说无限层了。

In a well-known episode of "Friends," Phoebe says to Rachel, “They don’t know we know they know we know. Joey, you can't say anything!"在著名美剧《老友记》的一集中，菲比对瑞秋说：“他们不知道我们知道他们知道我们知道。乔伊，你什么也不能说！”

And he replies, "I couldn't even if I wanted to!"乔伊回答：“我就算想说，也说不出来！”

Instead, common knowledge can be captured in a simple mental intuition that something is public or conspicuous or out there, and that can be conveyed by direct speech. In the case of our separated couple, a cell phone call. Indeed, solving coordination dilemmas may be the reason that language evolved in our species in the first place.实际上，“公共知识”可以通过一种简单的心理直觉来获得——某事是公开的、显而易见的、众所周知的——而这种状态可以通过直接的语言传递。在走散情侣的例子中，一个电话就足够了。事实上，解决协调困境可能正是人类语言最初演化的原因之一。

In the absence of a public event, the next best thing is conspicuous salience, or a focal point. Schelling suggests that our couple might gravitate toward the big clock in Grand Central Station, even if it wasn't particularly close to the point at which they'd been separated, simply because each might anticipate that it would pop into the mind of the other.如果没有公共事件，次优的选择是明显的“显著性”或“焦点”。谢林建议，这对情侣可能会选择去中央车站的大钟下见面，即使它离他们走散的地方并不近，仅仅是因为他们都可能想到对方会首先想到这个地方。

A third solution is a convention. A tacit agreement to do something in a certain way for no other reason than they have agreed to do it that way, which is reason enough. Our separated couple might agree that should they ever be separated in the future, they will adopt the convention of chivalry and go to the bookstore. Or patriarchy, and go to the camera store. Or whimsy, and go to a lost-and-found in a department store. Or fairness, and take turns or flip coins.第三种解决方式是“约定”。即双方默契地同意以某种方式行事，唯一的理由就是他们已经同意了这样做，而这本身就足够了。这对走散的情侣可能会约定，如果以后再走散，就按照“骑士精神”去书店；或者按照“男权主义”去相机店；又或者凭“异想天开”去百货商店的失物招领处；或者讲求“公平”，轮流决定或抛硬币来定。

Archaeological evidence indicates that ancient Egypt and Mesopotamia may have been in contact at least 10,000 years ago, when people in Mesopotamia began to farm and domesticate animals, and so making the transition from hunter-gatherers to an agricultural society. Many scholars believe that this social and technological revolution may have influenced similar developments in ancient Egypt, but there's been no irrefutable proof of direct contact between the populations until now.考古证据表明，古埃及文明和美索不达米亚文明可能早在一万年前就有过接触。当时，美索不达米亚人开始进行农垦并驯化动物，从而开启了从狩猎采集者向农耕社会的转变。许多学者相信，这一社会和技术变革可能影响了古埃及文明的类似发展进程，但此前还没有确凿的证据证明两个人群之间发生过直接接触。

Scientists have been using ancient DNA analysis to track changes in human evolution over millions of years, but refinements of the technique mean the technology now has the potential to show more recent historical events in a new way.科学家一直在用对人类远古 DNA 的分析来追踪人类在数百万年间的进化过程，但这项技术的改进意味着它现在有可能以一种新的方式呈现更近期的历史事件。

Surprisingly, severed tissues can survive for a few hours without these resources. And keeping them cool further slows the rate of tissue death, generally giving surgeons a 6-to-12-hour window for reattachment. But once the tissues die, reconnecting them won’t bring them back to life.令人惊讶的是，断裂的组织即使没有这些资源，也能存活几个小时。而将其保持低温则能进一步减缓组织坏死的速度，通常可以为外科医生争取 6 到 12 小时的再植时间。但一旦组织死亡，即使重新连接，也无法让它们“复活”。

This tight timeline is especially challenging for surgeons. Due to the issues we’ve already mentioned, reattachment operations are fairly uncommon. So most hospitals don’t have the tools and expertise required to tackle these time-sensitive procedures. And even if they do, nerve repair is extremely tricky. With perfectly clean cuts, surgeons can attempt to stitch nerves back together directly. And when a cut is ragged, they may try to create nerve conduits— tunnels between nerve ends that can allow the nerves to reconnect over time. But neither these, nor any other surgical options, reliably restore movement and sensation.这紧迫的时间限制对外科医生来说尤其具有挑战性。由于前面提到的种种问题，再植手术相当罕见，因此大多数医院并没有应对这种时间敏感型手术所需的工具和专业技术。即便具备条件，神经修复也是极其棘手的工作。在切口整齐的情况下，外科医生可以尝试直接将神经缝合；而如果切口参差不齐，他们可能会尝试制作“神经导管”——一种连接神经断端的隧道，使神经能够随着时间重新连接。但无论是这些方法还是其他手术手段，都无法确保可靠地恢复肢体的运动和感觉。

All these obstacles make it highly unlikely that a lost limb can be reattached. However, medical technology has developed another dependable solution for amputation: prosthetics. Today, prostheses come in countless forms to replace numerous body parts. Prosthetic legs are excellent for walking and running. Prosthetic arms have historically struggled to replicate our hands’ fine motor movements. However, new myoelectric prostheses can detect electrical activity in nearby muscles and then translate those signals into relatively precise movements.所有这些障碍使得断肢能够成功再植的可能性极低。然而，医学技术发展出了另一种可靠的截肢解决方案——假肢。如今，假肢的形式多种多样，可以替代人体的不同部位。假肢腿在行走和跑步方面表现出色；而假肢手臂在历史上一直难以复制人手的精细运动。然而，新的肌电假肢可以检测邻近肌肉的电活动，并将这些信号转化为相对精确的动作。

But perhaps the most dramatic development in prosthetic technology is transcutaneous osseointegration. First successfully performed in 1990, this procedure surgically anchors a metal implant into the bone of the remaining limb. The bone then grows into the crevices of the metal, creating a permanent connection. These implants extend through a portal in the skin, and can be attached to any prosthesis, which solves a handful of common prosthetic issues. Where traditional prosthetics can be heavy, providing a direct skeletal connection makes their weight feel more natural. Osseointegrated prosthetics are also less likely to irritate the skin where they attach, and they can offer more sensation by transmitting forces like vibration through the implant to the bone.或许，假肢技术中最引人注目的发展是“经皮骨整合”技术。该技术于 1990 年首次成功实施，它通过手术将金属植入物固定在残肢的骨骼中，随后骨骼会长入金属的缝隙中，从而形成永久连接。这些植入物会穿出皮肤的开口，并可以连接到任何假肢上，从而解决了许多传统假肢的常见问题。传统假肢可能较为笨重，而直接的骨骼连接能让重量感更加自然。经皮骨整合假肢也不易刺激与之接触的皮肤，并且能够通过将震动等力量从植入物传递到骨骼，为使用者提供更多的感知。

Even with all these new technologies, not everyone wants to replace or reattach a lost limb. After an amputation, some people opt to rely on their remaining limbs, with or without the help ofmobilityaids and other adaptive equipment.即便有了这些新技术，并不是每个人都希望替换或再植失去的肢体。截肢后，有些人选择依靠剩余的肢体生活，无论是否借助助行器或其他适应性设备。