Can You Step into the Same River Twice? 人能踏進同一條河兩次嗎？

🔊Heraclitus wrote in short, dense sayings, of which about a hundred and thirty survive as quotations in later authors. The most famous concern a river. “You cannot step twice into the same rivers; for fresh waters are ever flowing in upon you.” And, more strangely: “We step and do not step into the same rivers; we are and are not.” Plato reported the doctrine in the form that became proverbial, that “all things are in motion and nothing at rest,” and that “you cannot go into the same water twice.”

赫拉克利特用簡短而濃縮的格言寫作，其中大約一百三十條，以被後世作者引用的形式保存了下來。最有名的幾條談的是河。「你不能兩次踏進同一條河；因為新的水不斷地流到你身上。」還有更奇怪的一條：「我們踏進又沒有踏進同一條河；我們存在又不存在。」柏拉圖轉述這個學說，用的是後來成為諺語的形式：「萬物都在運動，沒有東西靜止」，以及「你不能兩次走進同樣的水」。

🔊It is easy to hear this as a denial that anything is ever the same, and one of his followers took it that way. Cratylus, according to Aristotle, criticized his master for saying that one cannot step twice into the same river, “for he thought one could not do it even once,” and in the end he gave up speaking and only moved his finger. But look at the first saying again. It speaks of the same rivers. Heraclitus does not deny that there is one river, the Cayster, into which the Ephesians stepped every day. His point is about what makes it one. Dam it, so that the water stops being replaced, and you no longer have a river. The sameness of the river consists in the exchange of its waters.

人很容易把這聽成是在否認任何東西曾經保持同一，而他的一位追隨者就是這樣理解的。照亞里斯多德的說法，克拉底魯批評老師說「人不能兩次踏進同一條河」，「因為他認為連一次都不行」；到最後他不再說話，只動動手指。但是再看一次第一句格言。它說的是「同一條河」。赫拉克利特並不否認有一條河，凱斯特河，以弗所人天天踏進去的那一條。他的重點在於：是什麼使它成為一條河？把它攔起來，讓水不再更替，你就不再有一條河了。河的同一，就在於它的水的更替。

🔊Heraclitus therefore taught more than flux. He taught that the flux is ordered. The world is “an ever-living Fire, with measures of it kindling, and measures going out,” and the word to notice is “measures.” Fire is his image for a thing that exists only by consuming and being fed, and a steady flame is a balance between the two. He called the principle of this balance the logos, a word that means both “account” and “proportion,” and he complained that people live as though they each had a private understanding when the logos is common to all. He saw the same balance in opposites. “The way up and the way down is one and the same.” Day and night, waking and sleeping, the bow’s wood pulling one way and its string the other: in each case two contrary things turn out to be one process seen from two sides. “The hidden attunement,” he said, “is better than the open.”

所以赫拉克利特教的不只是流變。他教的是：流變是有秩序的。世界是「一團永恆的活火，按一定的分寸燃燒，按一定的分寸熄滅」，要注意的詞是「分寸」。火是他用來比喻這樣一種東西的意象：它只有靠消耗與被餵養才存在；而穩定的火焰，是這兩者之間的平衡。他把這個平衡的原理稱為 logos，這個詞兼有「說明」與「比例」的意思；他抱怨說，人們活得好像各自有一套私人的理解，而 logos 其實是眾人共有的。他在對立的事物裡看到同樣的平衡。「上坡的路與下坡的路，是同一條路。」日與夜、醒與睡、弓的木頭往一邊拉而弦往另一邊拉：在每一種情形裡，兩個相反的東西，結果是同一個過程從兩面看過去的樣子。他說：「隱藏的和諧，勝過顯明的和諧。」

🔊Parmenides set out his view in a poem, in which a goddess reveals to him “the only two ways of search that can be thought of.” The first is “that It is, and that it is impossible for it not to be.” The second is “that It is not.” The second way, she says, cannot be followed at all: “For thou canst not know what is not—that is impossible—nor utter it; for it is the same thing that can be thought and that can be.” To think is to think of something. What is not, is nothing, and nothing is not there to be thought of.

巴門尼德用一首詩陳述他的看法；詩中有一位女神向他揭示「僅有的兩條可以設想的探究之路」。第一條是：「它存在，而且它不可能不存在。」第二條是：「它不存在。」女神說，第二條路根本走不通：「因為你無法認識不存在的東西——那是不可能的——也無法說出它；因為能被思想的與能存在的，是同一回事。」思想，就是思想到某個東西。不存在的就是無，而無並不在那裡供人思想。

🔊From this the rest follows with terrible ease. For a thing to come into being, it would have to come from what is not, and there is no such thing. For a thing to change, it would have to become what it is not. For there to be two things, there would have to be something between them that is not either of them. So what is “is uncreated and indestructible,” single, continuous, and unmoving. The changing world of the senses is an appearance that mortals have agreed to name. Parmenides’ pupil Zeno wrote the paradoxes of lesson A4 in order to show that those who laughed at this conclusion were worse off than his master.

由此，其餘的一切輕易得可怕地推了出來。一樣東西要生成，就得從不存在的東西而來，而沒有這樣的東西。一樣東西要改變，就得變成它所不是的。要有兩樣東西，它們之間就得有某個既不是這個、也不是那個的東西。所以存在者是「不生不滅的」，唯一、連續、不動。感官所見的那個變動的世界，是凡人約定命名出來的表象。巴門尼德的學生芝諾，寫下了 A4 那一課的悖論，為的是證明：嘲笑這個結論的人，處境比他的老師更糟。

🔊The next two centuries of Greek philosophy can be read as a series of attempts to grant Parmenides his premise and still keep the river. The atomists accepted that what truly exists never comes into being or perishes, and said that there are countless such things, atoms, whose rearrangement in empty space is what we call change. Plato divided the world in two. The Forms are as Parmenides described, eternal and unchanging, and they are what knowledge is about. The world we perceive is as Heraclitus described, and of it we have only opinion.

此後兩個世紀的希臘哲學，可以讀成一連串的嘗試：承認巴門尼德的前提，同時還把那條河保住。原子論者接受「真正存在的東西既不生成也不毀滅」，然後說：這樣的東西有無數個，就是原子；它們在虛空裡的重新排列，就是我們所說的變化。柏拉圖把世界一分為二。理型正如巴門尼德所描述的，永恆而不變，是知識的對象。我們感知的世界正如赫拉克利特所描述的，對它我們只有意見。

🔊Aristotle’s answer has lasted longest. He pointed out that “is not” is ambiguous. An acorn is not an oak, but it is not simply nothing either. It is potentially an oak. Change is the passage from being something potentially to being it actually, and it always has three terms: something that persists, a condition it lacked, and a condition it acquires. When a green leaf turns red, the leaf remains. Change, on this analysis, requires sameness. Parmenides was right that nothing comes from nothing, and wrong to think that change needs it to.

亞里斯多德的答案流傳得最久。他指出，「不是」是有歧義的。一顆橡實不是橡樹，但它也不是單純的「無」；它「潛在地」是一棵橡樹。變化，就是從「潛在地是某物」過渡到「現實地是某物」；它永遠有三項：一個持續存在的東西、一個它原本缺少的狀態、一個它後來獲得的狀態。綠葉變紅，葉子還在。照這個分析，變化需要同一。巴門尼德說「無中不能生有」是對的；他以為變化需要「無中生有」，那就錯了。

🔊At about the time Heraclitus was writing, Confucius stood beside a river and said: “What passes away is like this, is it not? It does not cease, day or night” (逝者如斯夫，不舍晝夜). The Analects gives no explanation, and readers have supplied two. One hears a sigh over time and mortality, the feeling that everything is carried off. The other, which became standard among the Neo-Confucians, hears admiration. The stream never rests, and the person who is learning should be like it. Both readings find in the river what Heraclitus found there. Heraclitus made a theory of the world from it, and the Chinese tradition took it as a lesson in how to live.

大約在赫拉克利特寫作的同時，孔子站在一條河邊說：「逝者如斯夫！不舍晝夜。」《論語》沒有給任何解釋，讀者補上了兩種。一種聽到的是對時間與生命有限的嘆息，覺得一切都被帶走了。另一種，後來成為宋明理學家的標準讀法，聽到的是讚嘆：這條水流從不停歇，求學的人應當像它。兩種讀法在河裡找到的，都是赫拉克利特在那裡找到的東西。赫拉克利特從它造出一套關於世界的理論，中國的傳統則把它當作一堂怎麼活的課。

🔊Neither side has gone away. Modern physics has a Parmenidean face. Its deepest laws are conservation laws, statements that some quantity stays the same through every change, and the theory of relativity is often read as describing a four-dimensional “block” in which past, present, and future are equally real and nothing flows at all. It also has a Heraclitean face. A flame, a whirlpool, a living cell, and a human body are stable patterns in a stream of matter and energy, and they exist only as long as the stream continues. If you take the first picture as basic you have to explain why we seem to experience change. If you take the second as basic you have to explain what it is that stays the same. The river is where the two questions meet, and that is why the saying is still quoted after twenty-five centuries.

兩邊都沒有消失。現代物理學有一張巴門尼德的臉。它最深的定律是守恆定律，也就是「某個量在一切變化中保持不變」的陳述；而相對論常被解讀為在描述一個四維的「塊體」，其中過去、現在、未來同樣真實，根本沒有任何東西在流動。它也有一張赫拉克利特的臉。火焰、漩渦、活細胞、人的身體，都是物質與能量之流裡的穩定樣式，只有在那道流持續的時候才存在。如果你把第一幅圖像當作根本，你就得解釋我們為什麼似乎經驗到變化。如果你把第二幅當作根本，你就得解釋保持同一的到底是什麼。河，就是這兩個問題相遇的地方；這就是為什麼這句話在兩千五百年後還在被引用。