悦读｜约翰·D.巴罗《不论——科学的极限和极限的科学》（双语）

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约翰·D.巴罗（John D. Barrow, 1952—2020），天体物理学家、著名科学作家。曾荣获洛克天文学奖和皇家格拉斯哥哲学学会开尔文奖章。他所创作的《宇宙的起源》（The Origin of the Universe, 1994）等15部科普作品被译为28种语言，受到读者的广泛欢迎。

译者李新洲为现任上海师范大学天体物理研究中心主任，第七届中国物理学会理事、第五届中国引力与相对论天体物理学会理事长、国际专业杂志《引力与宇宙学》（Gravitation and Cosmology）编委。或许纯粹的科学家能够给我们一个不同的思考角度，请大家一起欣赏。

（朗读：对外经济贸易大学卢铭）

Impossibility: The Limits of Science and the Science of Limits (Excerpt)

《不论——科学的极限和极限的科学》（节选）

By John D. Barrow

文/约翰·D.巴罗

译/李新洲

Preface

The Preface is the most important part of the book. Even reviewers read a preface.

—PHILIP GUEDALLA

前言

书籍之要在于序，评者亦善待之。

——菲利普·圭达拉

Both scientists and philosophers are much concerned with impossibilities. Scientists like to show that things widely held to be impossible are in fact entirely possible; philosophers, by contrast, are more inclined to demonstrate that things widely regarded as perfectly feasible are in fact impossible. Yet, paradoxically, science is only possible because some things are impossible.

哲学家和科学家都十分关注不可能性。科学家喜欢论证那些被广泛认为不可能的事物实际上都是完全可能的；与此相反，哲学家则倾向于去说明那些被广泛认为是可行的事物实际上是不可能的。然而事实上，科学之所以成为可能恰恰在于某些事物是不可能的。

The incontrovertible evidence that Nature is governed by reliable 'laws' allows us to separate the possible from the impossible. Only those cultures for whom there existed a belief that there was a distinction between the possible and the impossible provided natural breeding grounds for scientific progress. But 'impossibility' is not only about science. In the pages that follow we shall look at some of the ways in which the impossible in art, literature, politics, theology, and logic has stimulated the human mind to take unexpected steps: revealing how the concept of the impossible sheds new light on the nature and content of the actual. The idea of the impossible rings alarm bells in the minds of many.

自然界被一些可靠的“定律”所支配，而那些表明这一观点的无可置疑的证据容许我们将可能从不可能中分离出来。况且，只有那些认为可能与不可能之间存在明显差别的文化才能提供孕育科学进步的土壤。“不可能性”不仅仅涉及到科学。在接下来的篇章里我们将会看到，艺术、文学、政治和逻辑中的不可能性是如何促使人类意识发生惊人的进步：揭示不可能这一概念如何使现实事物的本质和内容更加清晰地表现出来。不可能这种观念在许多人的意识里都鸣响了警钟。

To some, any suggestion that there might be limits to the scope of human understanding of the Universe or to scientific progress is a dangerous meme that undermines confidence in the scientific enterprise. Equally uncritical, are those who enthusiastically embrace any suggestion that science might be limited because they suspect the motives and fear the dangers of unbridled investigation of the unknown.

对于一些人来说，任何宣称人类在对宇宙或科学进步的理解上存在极限的说法都会被认为是有损于我们对科学事业信念的危险信号。同样无可厚非的是，另一些人怀疑人类对未知领域过度探索的动机，并害怕由此而导致的危险，所以他们极力地赞同任何科学是有限的说法。

At the end of each century there seems to arise a stock-taking in science. We shall see that at the end of the last century the issue of the limits of science became a live one and attempts were made to pick out problems that could never be solved. These problems still make interesting reading. But what will people say about our concerns in a hundred years time? As we near the end of the twentieth century we look back on an extraordinary century of progress. Yet it is progress that possesses some extraordinary characteristics. A pattern has emerged in many spheres of inquiry in which a scientific theory becomes so successful in the quantity and quality of its accurate predictions that its practitioners start to wonder whether the end is in sight—whether their theory might be able to explain everything within its encompass. But then something strange happens. The theory predicts that it cannot predict. It turns out to be not simply limited in scope, but self-limiting. This pattern is so strikingly recurrent that it suggests to us that we can recognize mature scientific theories by their self-limiting character. Such limits arise not merely because theories are inadequate, inaccurate, or inappropriate: they tell us something profound about the nature of knowledge and the implications of investigating the Universe from within.

似乎在每个世纪末科学都会进行一次反思。我们将看到，在上个世纪末，科学的极限问题也曾是一个很活跃的问题，而且人们还试图去提出一些永远也不可能解决的问题。这些问题即使是现在看来依然十分有趣。但是，在一百年之后的今天我们该对我们所关注的事情说些什么呢？我们临近又一个世纪之末，要回首这个取得了非凡进步的世纪。显然，正是这种进步才使20世纪具备了非凡的特征。在人类许多认知领域中已经产生了一种模式，即，一种科学理论在定性和定量的准确预言方面取得巨大成功后，就会使其应用者们开始怀疑它是否有终结——他们的理论是否可以解释它所能包含的一切问题。随后，一些奇怪的事情发生了。理论自身预言了它是不可能预言所有一切的。由此得出的结论是，它的应用范围不是简单地受到限制，而是自我限制。这种模式惊人地一再重复出现，以至于我们可通过看是否具有自我限制的特征来判断某种理论是不是一种成熟的科学理论。这些极限的产生并不仅仅因为理论不充分、不准确或不恰当，它们进而告诉了我们一些关于知识本质和在宇宙内研究宇宙意味着什么的深层事物。

Our study of the limits of science and the science of limits will take us from the consideration of practical limits of cost, computability, and complexity to the restrictions imposed on what we can know by our location in the middle of the Nature's spectra of size, age, and complexity. We shall speculate about our possible technological futures and locate our current abilities on the spectrum of possibilities for the manipulation of Nature in the realms of the large, the small, and the complex. But practicalities are not the only limits we face. There may be limits imposed by the nature of our humanity. The human brain was not evolved with science in mind. Scientific investigation, like our artistic senses, are by-products of a mixed bag of attributes that survived preferentially because they were better adapted to survive in the environments they faced in the far distant past. Perhaps those ambiguous origins will compromise our quest for an understanding of the Universe? Next, we shall start to pick at the edges of possible knowledge. We shall learn that many of the great cosmological questions about the beginning, the end, and the structure of our Universe are unanswerable. Despite the confident exposition of the modern view of the Universe by astronomers, these expositions are invariably simplified in ways that disguise the reasons why we cannot know whether or not the Universe is finite or infinite, open or closed, of finite age or eternal. Finally, we delve into the mysteries of the famous theorems of Godel concerning the limitations of mathematics. We know that there must exist statements of arithmetic whose truth we can never confirm or deny. What does this really mean? What is the fine print on this theorem? What are its implications for science? Does it mean that there are scientific questions that we can never answer? We shall see that the answers are unexpected and lead us to consider the possible meaning of inconsistency in Nature, of the paradoxes of time travel, the nature of freewill and the workings of the mind. Finally, we shall explore some of the strange implications of trying to pass from the consideration of individual choices to collective choices. Whether it is the outcome of an election or the making up of one's mind in the face of the brain's competing options, we find a deep impossibility that may have ramifications throughout the domain of complex systems.

对于科学的极限和极限的科学的研究，把我们从对经费、可计算性和复杂性等现实极限的思考中带到了那些限制我们认知范围的约束上，而这些约束则是由我们处在自然界系列的中间位置所具有的尺度、年龄和复杂性造成的。我们将推断我们可能的技术前景，并且在处理自然界中大的、小的和复杂的领域的可能性系列上，对我们当前的能力进行定位。显然，现实性并不是我们所面临的唯一极限，此外还有人类本性所带来的极限。人类的大脑并不是为科学而进化的。科学研究就像我们的艺术鉴赏力一样，都是那些为了能更好地适应远古时期的环境而得以优先保留下来的具有各种特性的副产品。或许这些起源的模糊性将危及到我们理解宇宙的种种探索。接下来，我们将开始探索可求的知识的边缘。我们将了解到，那些关于宇宙的起源、终结和结构等重大的宇宙学问题都是不可回答的。尽管天文学家已经满怀信心地用现代宇宙观点做出了阐述，但这些阐述都做了简化，回避了我们不知道的问题：宇宙是有限还是无限的呢？开的还是闭的呢？有终结还是永恒的呢？此后，我们会探讨涉及到数学局限性的著名而神秘的哥德尔定理。我们了解到，肯定存在着这样一种算术陈述，其真实性是无法证明或证伪的。这究竟意味着什么？难道它意味着存在一些我们永远都不能回答的科学问题吗？我们将看到对此问题的回答是出人意料的，并且还会促使我们去思考自然界的不自洽性、时间旅行悖论、自由意志的本性以及意识的工作机理等一些问题的可能含义。最后，在试图把个体的选择依次传递给集体的选择时，我们将探索其中所隐含的一些奇怪的东西，不论是一次选举的结果，还是当存在几种选择时所做出的决定，我们都发现了一种在整个复杂系统领域中起作用的深邃的不可能性。

Here, in this strange world of fundamental limits we learn that worlds that are complex enough for certain individualities to be manifest necessarily display an open-endedness that defies capture within the confines of a single logical system. Universes that are complex enough to give rise to consciousness impose limits on what can be known about them from within.

在这个由一些基本极限所构成的奇异世界里，我们知道，那些复杂得足以必然地表现出某些个性的世界展示出一种开放式的终结，而这是一个单一的逻辑体系所不能描述的。复杂得足以产生意识的宇宙，对于身处其内的我们能知道些什么也做了限制。

By the end of our journey, I hope the reader will have come to see that there is more to impossibility than first meets the eye. Its role in our understanding of things is far from negative. Indeed, I believe that we will gradually come to appreciate that the things that cannot be known, that cannot be done, and cannot be seen, define our Universe more clearly, more completely, and more sharply than those that can.

在我们旅程的终点，我希望读者能够认识到，不可能性比我们初看起来具有更多的内涵。在我们理解事物的过程中，它并非只起负面的作用。事实上，我相信我们将会逐渐地接受，不可知、不可为以及不可见，会比可知、可为以及可见，更加清晰、完整和鲜明地定义我们的宇宙。

Brighton November 1997

J. D. B.

1997年11月于布莱顿

J. D. B.

对外经济贸易大学英语学院实习生

卢铭整理