Is It Still the Same Ship? 這還是同一艘船嗎？

🔊Both sides have a case. Those who say it is the same ship can point out that there was never a day on which Athens had no ship of Theseus. A single plank was changed, and the ship with one new plank was surely the ship that had been there the day before. The next repair was no different. If the ship survives each step, it survives all of them. Those who say it is not the same can point to the result. Not one splinter that Theseus touched is left. A thing made wholly of timber he never saw can be a faithful replica of his ship, and a replica is a different thing from the original.

雙方都有道理。主張是同一艘船的人可以指出：雅典從來沒有哪一天是沒有特修斯之船的。換掉了一塊木板，而換了一塊新木板的船，當然就是前一天在那裡的那艘船。下一次修補也沒有什麼不同。如果這艘船撐得過每一步，它就撐得過全部的步驟。主張不是同一艘的人可以指著結果說：特修斯碰過的木頭，連一根碎片都不剩。一個完全用他從沒見過的木料做成的東西，可以是他那艘船的忠實複製品，而複製品跟原物是兩樣東西。

🔊In 1655 Thomas Hobbes added a twist that turned an old puzzle into a hard one. Suppose that someone had kept the old planks as they were taken out, and afterward put them together again in the same order. Now there are two ships. One stands in the harbor, where the ship of Theseus has always stood, and it grew out of the original by gradual repair. The other stands in a warehouse, and it is made of exactly the planks that Theseus sailed on, arranged as they were. Each has a strong claim to be the original. They cannot both be, since one ship cannot be in two places. And it seems arbitrary to say that neither is.

1655 年，霍布斯加了一個轉折，把一個古老的謎題變成了一個難題。假設有人把舊木板在拆下來的時候都留著，事後再照原來的次序把它們組起來。現在有兩艘船了。一艘停在港裡，就在特修斯之船一向停泊的地方，它是由原船經過逐步修補而來的。另一艘在倉庫裡，它恰恰是用特修斯航行時的那些木板、照原樣排列做成的。兩艘都有很強的理由自稱是原船。它們不可能都是，因為一艘船不可能在兩個地方。而說兩艘都不是，又似乎很武斷。

🔊Some care with words is needed first. Two coins from the same mint are the same in one sense, since they are exactly alike, and are plainly two coins. Philosophers call that qualitative identity. The puzzle concerns the other sense, numerical identity, being one and the same thing. The repaired ship and the original are certainly not alike in every respect. The question is whether they are one thing or two. Numerical identity obeys a strict logic. If A is the same thing as B, and B is the same thing as C, then A is the same thing as C. That is why Hobbes’s version hurts. If the ship in the harbor is the original, and the ship in the warehouse is the original, then the two are one ship, which is absurd.

首先得在用詞上小心一點。同一個鑄幣廠出來的兩枚硬幣，在某個意義上是「一樣的」，因為它們一模一樣，但明明是兩枚硬幣。哲學家把那稱為「質的同一」。這個謎題關心的是另一個意思：「數的同一」，也就是「是同一個東西」。修補過的船與原船，肯定不是在每個方面都一樣。問題是：它們是一個東西，還是兩個？數的同一遵守嚴格的邏輯。如果 A 與 B 是同一個東西，B 與 C 是同一個東西，那麼 A 與 C 就是同一個東西。這就是霍布斯的版本讓人難受的原因：如果港裡的船是原船，倉庫裡的船也是原船，那麼這兩艘就是一艘船，而這是荒謬的。

🔊The first answer says that a thing is its matter. On this view the warehouse ship is the original, and the harbor ship is a new vessel that came into being plank by plank. Strictly applied, the view implies that nothing survives the loss of a single part, so that you are not the person who began reading this sentence. Few can live with that. The second answer says that a thing is its form and its continuous history. Aristotle held that what makes a ship a ship is its organization, and Locke made the same point about living things: “their identity depends not on a mass of the same particles, but on something else,” so that an oak is the same plant from seedling to great tree “as long as it partakes of the same life.” On this view the harbor ship wins.

第一個答案說，一樣東西就是它的材料。照這個看法，倉庫裡的船才是原船，港裡的船是一塊木板一塊木板逐漸形成的新船。嚴格應用的話，這個看法蘊涵：任何東西只要失去一個部分，就不復存在；所以你已經不是開始讀這個句子的那個人了。很少有人受得了這個結論。第二個答案說，一樣東西就是它的形式與它連續的歷史。亞里斯多德主張，使船成為船的是它的組織結構；洛克對生物提出了同樣的論點：「它們的同一性不依賴於同一堆微粒，而是依賴於別的東西」，所以一棵橡樹從幼苗長成大樹，始終是同一株植物，「只要它分有同一個生命」。照這個看法，港裡的船贏了。

🔊The third answer changes the picture. Suppose a ship is extended in time as well as in space, a long four-dimensional thing of which each day’s ship is a slice. Then the question of which later ship is the earlier one was badly put. There are two overlapping histories that share their early stages and divide, as two roads may share a stretch of pavement. The fourth answer is the most deflating. It says that there is no further fact to discover. We know everything that happened to every plank. What remains is a decision about how to use the word “same,” and the decision properly depends on our purposes. A museum, an insurer, and a navy may each be right to count differently.

第三個答案換了一幅圖像。假設一艘船除了在空間裡延展，也在時間裡延展，是一個長長的四維的東西，每一天的船只是它的一個切片。那麼「後來的哪一艘船是先前的那一艘」這個問題，本來就問得不好。有兩段重疊的歷史，它們共用早期的階段，然後分開，就像兩條路可以共用一段路面。第四個答案最洩氣。它說，沒有進一步的事實等著被發現。每一塊木板發生了什麼，我們全都知道。剩下的是一個決定：怎麼使用「同一」這個詞；而這個決定理當取決於我們的目的。博物館、保險公司與海軍，各自用不同的算法，可以都是對的。

🔊The puzzle is acted out in real institutions, and different cultures have settled it differently. At Ise in Japan, the principal shrine buildings are torn down and rebuilt on an adjoining plot every twenty years, in new cypress, to the same plan. This has been done more than sixty times since the seventh century. Nobody in Japan thinks that the shrine is twenty years old. Its identity is taken to lie in the form, the site, and the unbroken practice of the carpenters. European conservation long took the opposite view and prized original material above all, so that a restored cathedral was thought to have lost something a ruin kept. In 1994 an international meeting of conservators at Nara, prompted by cases like Ise, agreed that authenticity cannot be judged by one fixed standard and must be understood within each culture. The United States Navy keeps a wooden frigate of 1797, the Constitution, in commission, and only a small fraction of her timber is original. She is still the same ship in the eyes of the law.

這個謎題在真實的制度裡不斷上演，而不同的文化用不同的方式解決它。在日本的伊勢，主要的神宮建築每二十年就拆掉，在相鄰的空地上用新的檜木、照同樣的規制重建。從七世紀以來，這已經做了六十多次。在日本，沒有人認為這座神宮只有二十年的歷史。它的同一性被認為在於形制、地點，以及匠人從未中斷的技藝傳承。歐洲的文物保存長期採取相反的看法，把原始材料看得高於一切，所以人們認為，一座修復過的大教堂失去了某種廢墟還保有的東西。1994 年，一場在奈良召開的國際文物保存會議，在伊勢這類案例的推動下，達成了共識：真實性不能用單一固定的標準來判斷，必須放在各個文化之內來理解。美國海軍讓一艘 1797 年的木造巡防艦「憲法號」保持現役，而她的木料只有一小部分是原件。在法律眼中，她仍然是同一艘船。

🔊The reason the puzzle has lasted is that it is about us. A human body exchanges matter with its surroundings continuously. Most of the atoms in it are replaced within a few years, though some cells, including most of the neurons in the cerebral cortex, last a lifetime. If matter were the standard of identity, the person who was promised something ten years ago would no longer exist to collect it, and the person who committed a crime could not be punished. We hold each other to promises and debts across decades, and so in practice we have all taken the side of form and continuity. Whether we are entitled to is the subject of later lessons on the self.

這個謎題之所以流傳至今，是因為它談的就是我們。人的身體不斷地跟周遭交換物質。體內大部分的原子在幾年之內就被替換掉了，雖然有些細胞，包括大腦皮質裡大多數的神經元，會存續一輩子。如果材料是同一性的標準，那麼十年前被許下承諾的那個人，就不復存在、無從兌現了；犯了罪的那個人，也無法受罰。我們隔著幾十年，仍然要彼此對承諾與債務負責；所以在實踐上，我們全都站到了「形式與連續性」這一邊。至於我們有沒有資格這樣做，是後面談「自我」的幾課的主題。

🔊Zhuangzi has an image for the unease this causes. A man hides his boat in a ravine and thinks it safe, “yet at midnight a strong man carries it off on his back, and the sleeper knows nothing of it.” The strong man is change. One reading of the passage is that nothing stays hidden from it for even a night, and that the boat we find in the morning has already ceased to be the boat we hid.

對於這件事引起的不安，莊子有一個意象。一個人把船藏在山谷裡，以為很牢靠，「然而夜半有力者負之而走，昧者不知也」。那個有力者就是變化。這段話的一種讀法是：沒有任何東西能躲開它，連一夜都躲不過；我們早上找到的那艘船，已經不是我們藏起來的那一艘了。