Thought experiments are mental concepts or hypotheses, often resembling riddles, which are used by philosophers and scientists as simple ways of illuminating what are usually very dense ideas. Most often, they’re used in more abstract fields like philosophy and theoretical physics, where physical experiments aren’t possible. They serve as some hearty food for thought, but given their complex subject matter, it’s not unusual for even the thought experiment itself to be nearly incomprehensible. With this in mind, here are ten of the most famous thought experiments, along with explanations of the philosophical, scientific, and ethical ideas they work to explain:
思想實驗是一種精神上的觀念或假想,通常和謎語相似,是哲學家和科學家用以瞭解什麼是大眾思想的一種簡單方法。他們的運用在如哲學和理論物理(理論物理無需做實驗)等抽象領域是最為廣泛的。他們像是為思想準備的一份大餐,最終給出複雜的答案。即使思想實驗本身也會有無法理解的時候,這並不奇怪。下面是 10個著名的思想實驗,還有他們所要表達的哲學、科學和倫理意義。
10.電車難題(The Trolley Problem)
One of the most well known thought experiments in the field of ethics is the “Trolley Problem,” which goes something like this: a madman has tied five innocent people to a trolley track. An out of control trolley car is careening toward them, and is moments away from running them over. Luckily, you can pull a lever and divert the trolley to another track. The only problem is that the madman has also tied a single person to that track. Considering the circumstances, should you pull the lever?
What it Means:
The trolley problem was first proposed by the philosopher Philippa Foot as a means of critiquing the major theories in ethical philosophy, in particular utilitarianism, the system which proposes that the most moral decision is always the one that provides “the greatest good for the greatest number.” From a utilitarian point of view, the obvious choice is to pull the lever, saving five and only killing one. But critics of this theory would state that in pulling the lever you become complicit in what is clearly an immoral act—you are now partially responsible for the death of the lone person on the other track. Others, meanwhile, argue that your mere presence in the situation demands that you act, and that to do nothing would be equally immoral. In short, there is no wholly moral action, and this is the point. Many philosophers have used the trolley problem as an example of the ways that real world situations often force individuals to compromise their own moral codes, and that there are times when there is no totally moral course of action.
「電車難題」是倫理學領域最為知名的思想實驗之一,其內容大致是:一個瘋子把五個無辜的人綁在電車軌道上。一輛失控的電車朝他們駛來,並且片刻後就要碾壓到他們。幸運的是,你可以拉一個拉杆,讓電車開到另一條軌道上。但是還有一個問題,那個瘋子在那另一條軌道上也綁了一個人。考慮以上狀況,你應該拉杆嗎?
電車難題最早是由哲學家Philippa Foot提出的,用來批判倫理哲學中的主要理論,特別是功利主義。功利主義提出的觀點是,大部分道德決策都是根據「為最多的人提供最大的利益」的原則做出的。從一個功利主義者的觀點來看,明顯的選擇應該是拉拉杆,拯救五個人只殺死一個人。
但是功利主義的批判者認為,一旦拉了拉杆,你就成為一個不道德行為的同謀——你要為另一條軌道上單獨的一個人的死負部分責任。然而,其他人認為,你身處這種狀況下就要求你要有所作為,你的不作為將會是同等的不道德。總之,不存在完全的道德行為,這就是重點所在。許多哲學家都用電車難題作為例子來表示現實生活中的狀況經常強迫一個人違背他自己的道德準則,並且還存在著沒有完全道德做法的情況。
9.空地上的奶牛(The Cow in the field)

One of the major thought experiments in epistemology (the field of philosophy that deals with knowledge) is what is known as “The Cow in the Field.” It concerns a farmer who is worried his prize cow has wandered off. When the milkman comes to the farm, he tells the farmer not to worry, because he’s seen that the cow is in a nearby field. Though he’s nearly sure the man is right, the farmer takes a look for himself, sees the familiar black and white shape of his cow, and is satisfied that he knows the cow is there. Later on, the milkman drops by the field to double-check. The cow is indeed there, but it’s hidden in a grove of trees. There is also a large sheet of black and white paper caught in a tree, and it is obvious that the farmer mistook it for his cow. The question, then: even though the cow was in the field, was the farmer correct when he said he knew it was there?
What it Means:
The Cow in the Field was first used by Edmund Gettier as a criticism of the popular definition of knowledge as “justified true belief”—that is, that something becomes knowledge when a person believes it; it is factually true; and they have a verifiable justification for their belief. In the experiment, the farmer’s belief that the cow was there was justified by the testimony of the milkman and his own verification of a black and white object sitting in the field. It also happened to be true, as the milkman later confirmed. But despite all this, the farmer did not truly know the cow was there, because his reasoning for believing it turned out to be based on false premises. Gettier used this experiment, along with a few other examples, as proof of his argument that the definition of knowledge as justified true belief needed to be amended.
認知論領域的一個最重要的思想實驗就是「空地上的奶牛」。它描述的是,一個農民擔心自己的獲獎的奶牛走丟了。這時送奶工到了農場,他告訴農民不要 擔心,因為他看到那頭奶牛在附件的一塊空地上。雖然農民很相信送奶工,但他還是親自看了看,他看到了熟悉的黑白相間的形狀並感到很滿意。過了一會,送奶工 到那塊空地上再次確認。那頭奶牛確實在那,但它躲在樹林裏,而且空地上還有一大張黑白相間的紙纏在樹上,很明顯,農民把這張紙錯當成自己的奶牛了。問題是 出現了,雖然奶牛一直都在空地上,但農民說自己知道奶牛在空地上時是否正確?
空地上的奶牛最初是被 Edmund Gettier 用來批判主流上作為知識的定義的JTB(justified true belief)理論,即當人們相信一件事時,它就成為了知識;這件事在事實上是真的,並且人們有可以驗證的理由相信它。在這個實驗中,農民相信奶牛在空地上,且被送奶工的證詞和他自己對於空地上的黑白相間物的觀察所證實。而且經過送奶工後來的證實,這件事也是真實的。儘管如此,農民並沒有真正的知道奶牛在那兒,因為他認為奶牛在那兒的推導是建立在錯誤的前提上的。Gettier利用這個實驗和其他一些例子,解釋了將知識定義為JTB的理論需要修正。
8.定時炸彈(The Ticking Time Bomb)
If you’ve paid any attention to political discourse over the past few years—or ever seen an action movie, for that matter—then you are no doubt familiar with the “ticking time bomb” thought experiment. It asks you to imagine that a bomb or other weapon of mass destruction is hidden in your city, and the timer on it will soon strike zero. You have in your custody a man with knowledge of where the device is planted. Do you resort to torture in order to get him to give up the information?
What it Means:
Like the trolley problem, the ticking time bomb scenario is an ethical problem that forces one to choose between two morally questionable acts. It is most often employed as a counter argument to those who say the use of torture is inexcusable under any circumstances. It’s also used as an example of the way laws—like those the U.S. has against torturing prisoners—will always be set aside given extreme circumstances. Thanks to its fictionalized use in television shows like 24, along with its constant position in political debates, the ticking time bomb scenario has become one of the most frequently repeated thought experiments. An even more extreme take on the problem was presented in a British news article earlier this year. That version proposes that the terrorist in question won’t respond to torture, and asks if one would be willing to resort to torturing the man’s wife and children as a means of extracting the information from him.
如果你關注近幾年的政治時事,或者看過動作電影,那麼你對於「定時炸彈」思想實驗肯定很熟悉。它要求你想像一個炸彈或其他大規模殺傷性武器藏在你的城市中,並且爆炸的倒計時馬上就到零了。在羈押中有一個知情者,他知道炸彈的埋藏點。你是否會使用酷刑來獲取情報?
與電車難題類似,定時炸彈情景也是強迫一個人從兩個不道德行徑中選擇的倫理 問題。它一般被用作對那些說在任何情況下都不能使用酷刑的反駁。它也被用作在極端形勢下法律——就像美國的嚴禁虐囚的法律——可以被放在第二位的例子。歸 功於像《24小時》的電視節目和各種政治辯論,定時炸彈情景已成為最常引用的思想實驗之一。今年早些時候,一份英國報紙提出了更為極端的看法。這份報紙提 議說,如果那個恐怖分子對酷刑毫無反應,那麼當局者是否願意拷打他的妻子兒女來獲取情報。
7.愛因斯坦的光線(Einstein’s Light Beam)
It’s a little known fact that Albert Einstein’s famous work on special relativity was spurred by a thought experiment he conducted when he was only 16 years old. In his book Autobiographical Notes, Einstein recalls how he once daydreamed about chasing a beam of light as it traveled through space. He reasoned that if he were able to move next to it at the speed of light, he should be able to observe the light frozen in space as “an electromagnetic field at rest though spatially oscillating.” For Einstein, this thought experiment proved that for his imaginary observer “everything would have to happen according to the same laws as for an observer who, relative to the Earth, was at rest.”
What it Means:
In truth, no one really knows for sure. Scientists have long debated how this deceivingly simple thought experiment helped Einstein make the massive theoretical leap required to arrive at special relativity theory. At the time, the ideas in the experiment contradicted the now-debunked belief in the “aether,” an invisible field through which light was believed to travel. It would be years before he could prove he was right, but this thought experiment was somehow the “germ,” as he called it, for Einstein’s theory of special relativity, one of the ideas that first established him as a towering figure in theoretical physics.
愛因斯坦著名的狹義相對論是受啟於他16歲做的思想實驗。在他的自傳中,愛因斯坦回憶道他當時幻想在宇宙中追尋一道光線。他推理說,如果他能夠以光速在光線旁邊運動,那麼他應該能夠看到光線成為“在空間上不斷振盪但停滯不前的電磁場”。對於愛因斯坦,這個思想實驗證明了對於這個虛擬的觀察者,所有的物理定律應該和一個相對於地球靜止的觀察者觀察到的一樣。
事實上,沒人確切知道這意味著什麼。科學家一直都在爭論一個如此簡單的思想實驗是如何幫助愛因斯坦完成到狹義相對論這如此巨大的飛躍的。在當時,這個實驗中的想法與現在已被拋棄的“以太”理論相違背。但他經過了好多年才證明了自己是正確的。
6.特修斯之船(The Ship of Theseus)
One of the oldest of all thought experiments is the paradox known as the Ship of Theseus, which originated in the writings of Plutarch. It describes a ship that remained seaworthy for hundreds of years thanks to constant repairs and replacement parts. As soon as one plank became old and rotted, it would be replaced, and so on until every working part of the ship was no longer original to it. The question is whether this end product is still the same Ship of Theseus, or something completely new and different. If it’s not, at what point did it stop being the same ship? The Philosopher Thomas Hobbes would later take the problem even further: if one were to take all the old parts removed from the Ship of Theseus and build a new ship from them, then which of the two vessels is the real Ship of Theseus?What it Means:
For philosophers, the story of the Ship of Theseus is used as a means of exploring the nature of identity, specifically the question of whether objects are more than just the sum of their parts. A more modern example would be a band that had evolved over the years to the point that few or no original members remained in the lineup. This notion is also applicable to everything from businesses, which might retain the same name despite mergers and changes in leadership, to the human body, which is constantly regenerating and rebuilding itself. At its heart, the experiment forces one to question the commonly held idea that identity is solely contained in physical objects and phenomena.
最為古老的思想實驗之一。最早出自普魯塔克的記載。它描述的是一艘可以在海上航行幾百年的船,歸功於不間斷的維修和替換部件。只要一塊木板腐爛 了,它就會被替換掉,以此類推,直到所有的功能部件都不是最開始的那些了。問題是,最終產生的這艘船是否還是原來的那艘特修斯之船,還是一艘完全不同的 船?如果不是原來的船,那麼在什麼時候它不再是原來的船了?哲學家Thomas Hobbes後來對此進來了延伸,如果用特修斯之船上取下來的老部件來重新建造一艘新的船,那麼兩艘船中哪艘才是真正的特修斯之船?
對於哲學家,特修斯之船被用來研究身份的本質。特別是討論一個物體是否僅僅 等於其組成部件之和。一個更現代的例子就是一個不斷發展的樂隊,直到某一階段樂隊成員中沒有任何一個原始成員。這個問題可以應用於各個領域。對於企業,在 不斷並購和更換東家後仍然保持原來的名字。對於人體,人體不間斷的進行著新陳代謝和自我修復。這個實驗的核心思想在於強迫人們去反思身份僅僅局限在實際物體和現象中這一常識。