探索的动机 ——在普朗克六十岁生日庆祝会上的讲话

欧凯财税

探索的动机 ——在普朗克六十岁生日庆祝会上的讲话

- 爱因斯坦 -

这是爱因斯坦于1918年4月在柏林物理学会举办的麦克斯·普朗克六十岁生日庆祝会上的讲话。讲稿最初发表在1918年出版的《庆祝麦克斯·普朗克60寿辰：德国物理学会演讲集》。1932年爱因斯坦将此文略加修改，作为普朗克文集《科学往何处去》的序言。

       在科学的庙堂里有许多房舍，住在里面的人真是各式各样，而引导他们到那里去的动机实在也各不相同。有许多人爱好科学是因为科学给他们以超乎常人的智力上的快感，科学是他们自己的特殊娱乐，他们在这种娱乐中寻求生动活泼的经验和雄心壮志的满足；在这座庙堂里，另外还有许多人所以把他们的脑力产物奉献在祭坛上，为的是纯粹功利的目的。如果上帝有位天使跑来把所有属于这两类的人都赶出庙堂，那末聚集在那里的人就会大大减少，但是，仍然会有一些人留在里面，其中有古人，也有今人。我们的普朗克就是其中之一，这也就是我们所以爱戴他的原因。

    我很明白，我们刚才在想象中随便驱逐了许多卓越的人物，他们对建设科学庙堂有过很大的也许是主要的贡献；在许多情况下我们的天使也会觉得难以做出决定。但有一点我可以肯定，如果庙堂里只有我们刚才驱逐了的那两类人，那末这座庙堂就决不会存在，正如只有蔓草就不成其为森林一样。因为，对于这些人来说，只要有机会，人类活动的任何领域他们都会去干：他们究竟成为工程师，官吏，商人，还是科学家，完全取决于环境。现在让我们再来看看那些为天使所宠爱的人吧。

    他们大多数是相当怪僻、沉默寡言和孤独的人，但尽管有这些共同特点，实际上他们彼此之间很不一样，不象被赶走的那许多人那样彼此相似。究竟是什么力量把他们引到这座庙堂里来的呢？这是一个难题，不能笼统地用一句话来回答。首先我同意叔本华（Schopenhauer）所说的，把人们引向艺术和科学的最强烈的动机之一，是要逃避日常生活中令人厌恶的粗俗和使人绝望的沉闷，是要摆脱人们自己反复无常的欲望的桎梏。一个修养有素的人总是渴望逃避个人生活而进入客观知觉和思维的世界；这种愿望好比城市里的人渴望逃避喧嚣拥挤的环境，而到高山上享受幽寂的生活，在那里，透过清寂而纯洁的空气，可以自由地眺望，陶醉于那似乎是为永恒而设计的宁静景色。

   除了这种消极的动机以外，还有一种积极的动机。人们总想以最适当的方式来画出一幅简化的和易领悟的世界图像，于是他就试图用他的这种世界体系（cosmos）来代替经验的世界，并来征服它。这就是画家、诗人、思辨哲学家和自然科学家所做的。他们都按自己的方式去做。各人都把世界体系及其构成作为他的感情生活的支点，以便由此找到他在个人经验的狭小范围内所不能找到的宁静和安定。

    理论物理学家的世界图像在所有这些可能的图像中占有什么地位呢？它在描述各种关系时要求尽可能达到最高标准的严格精确性，这样的标准只有用数学语言才能达到。另一方面，物理学家对于他的主题必须极其严格地加以限制，他必须满足于描述我们的经验领域里的最简单事件；企图以理论物理学家所要求的精密性和逻辑完备性来重现一切比较复杂的事件，这不是人类智力所能及的。高度的纯粹性、明晰性和确定性要以完整性为代价。但是当人们畏缩而胆怯地不去管一切不可捉摸和比较复杂的东西时，那末能吸引我们去认识自然界的这一渺小部分的究竟又是什么呢？难道这种谨小慎微的努力结果也够得上宇宙理论的美名吗？

    我认为，是够得上的；因为，作为理论物理学结构基础的普遍定律，应当对任何自然现象都有效。有了它们，就有可能借助于单纯的演绎得出一切自然过程（包括生命）的描述，也就是说得出关于这些过程的理论，只要这种演绎过程并不太多地超出人类理智能力。因此，物理学家放弃他的世界体系的完整性，倒不是一个什么根本原则性的问题。

     物理学家的最高使命是要得到那些普遍的基本定律，由此世界体系就能用单纯的演绎法建立起来。要通向这些定律，并没有逻辑的道路，只有通过那种以对经验的共鸣的理解为依据的直觉，才能得到这些定律。由于有这种方法论上的不确定性，人们可以假定，会有许多个同样站得住脚的理论物理体系，这个看法在理论上无疑是正确的。但是，物理学的发展表明，在某一时期里，在所有可想到的解释中，总有一个显得比别的都要高明得多。凡是真正深入研究过这问题的人，都不会否认唯一决定理论体系的，实际上是现象世界，尽管在现象和他们的理论原理之间并没有逻辑的桥梁；这就是莱布尼兹（Leibnitz）非常中肯地表述过的“先定的和谐”。物理学家往往责备认识论者对这个事实没有给予足够的注意。我认为，几年前马赫同普朗克之间所进行的论战的根源就在于此。

    渴望看到这种先定的和谐，是无穷的毅力和耐心的源泉。我们看到，普朗克就是因此而专心致志于这门科学中的最普遍的问题，而不使自己分心于比较愉快的和容易达到的目标上去。我常常听到同事们试图把他的这种态度归因于非凡的意志力和修养，但我认为这是错误的。促使人们去做这种工作的精神状态是同信仰宗教的人或谈恋爱的人的精神状态相类似的；他们每天的努力并非来自深思熟虑的意向或计划，而是直接来自激情。我们敬爱的普朗克就坐在这里，内心在笑我像孩子一样提着第欧根尼的灯闹着玩。我们对他的爱戴不需要作老生常谈的说明，祝愿他对科学的热爱继续照亮他未来的道路，并引导他去解决今天物理学的最重要的问题，这问题是他自己提出来的，并且为了解决这问题他已经做了很多工作。祝他成功地把量子论同电动力学和力学统一于一个单一的逻辑体系里。

PRINCIPLES OF RESEARCH

Address by Albert Einstein (1918)

               (Physical Society, Berlin, for Max Planck's sixtieth birthday)

      Address delivered at a celebration of Max Planck’s sixtieth birthday (1918) before the Physical Society in Berlin. Published in Mein Weltbild, Amsterdam: Querido Verlag, 1934. Max Planck (1858—1947) was for many years professor of theoretical physics at the University of Berlin. By fare the most outstanding of his contributions to physics is his quantum theory, which he advanced in 1900 and which has provided the basis for the whole development of modern a tomic physics. Next to Planck it was Einstein who did the pioneering work in the young field, above all in his theory of specific heats (1907). It was he who perceived more than anyone else the fundamental and pervasive character of quantum concept in all its ramifications.

      IN the temple of science are many mansions, and various indeed are they that dwell therein and the motives that have led them thither. Many take to science out of a joyful sense of superior intellectual power; science is their own special sport to which they look for vivid experience and the satisfaction of ambition; many others are to be found in the temple who have offered the products of their brains on this altar for purely utilitarian purposes. Were an angel of the Lord to come and drive all the people belonging to these two categories out of the temple, the assemblage would be seriously depleted, but there would still be some men, of both present and past times, left inside. Our Planck is one of them, and that is why we love him.

      I am quite aware that we have just now lightheartedly expelled in imagination many excellent men who are largely, perhaps chiefly, responsible for the buildings of the temple of science; and in many cases our angel would find it a pretty ticklish job to decide. But of one thing I feel sure: if the types we have just expelled were the only types there were, the temple would never have come to be, any more than a forest can grow which consists of nothing but creepers. For these people any sphere of human activity will do, if it comes to a point; whether they become engineers, officers, tradesmen, or scientists depends on circumstances. Now let us have another look at those who have found favor with the angel. Most of them are somewhat odd, uncommunicative, solitary fellows, really less like each other, in spite of these common characteristics, than the hosts of the rejected. What has brought them to the temple? That is a difficult question and no single answer will cover it. To begin with, I believe with Schopenhauer that one of the strongest motives that leads men to art and science is escape from everyday life with its painful crudity and hopeless dreariness, from the fetters of one's own ever shifting desires. A finely tempered nature longs to escape from personal life into the world of objective perception and thought; this desire may be compared with the townsman's irresistible longing to escape from his noisy, cramped surroundings into the silence of high mountains, where the eye ranges freely through the still, pure air and fondly traces out the restful contours apparently built for eternity.

     With this negative motive there goes a positive one. Man tries to make for himself in the fashion that suits him best a simplified and intelligible picture of the world; he then tries to some extent to substitute this cosmos of his for the world of experience, and thus to overcome it. This is what the painter, the poet, the speculative philosopher, and the natural scientist do, each in his own fashion. Each makes this cosmos and its construction the pivot of his emotional life, in order to find in this way the peace and security which he cannot find in the narrow whirlpool of personal experience.

     What place does the theoretical physicist's picture of the world occupy among all these possible pictures? It demands the highest possible standard of rigorous precision in the description of relations, such as only the use of mathematical language can give. In regard to his subject matter, on the other hand, the physicist has to limit himself very severely: he must content himself with describing the most simple events which can be brought within the domain of our experience; all events of a more complex order are beyond the power of the human intellect to reconstruct with the subtle accuracy and logical perfection which the theoretical physicist demands. Supreme purity, clarity, and certainty at the cost of completeness. But what can be the attraction of getting to know such a tiny section of nature thoroughly, while one leaves everything subtler and more complex shyly and timidly alone? Does the product of such a modest effort deserve to be called by the proud name of a theory of the universe?

      In my belief the name is justified; for the general laws on which the structure of theoretical physics is based claim to be valid for any natural phenomenon whatsoever. With them, it ought to be possible to arrive at the description, that is to say, the theory, of every natural process, including life, by means of pure deduction, if that process of deduction were not far beyond the capacity of the human intellect. The physicist's renunciation of completeness for his cosmos is therefore not a matter of fundamental principle.
The supreme task of the physicist is to arrive at those universal elementary laws from which the cosmos can be built up by pure deduction. There is no logical path to these laws; only intuition, resting on sympathetic understanding of experience, can reach them. In this methodological uncertainty, one might suppose that there were any number of possible systems of theoretical physics all equally well justified; and this opinion is no doubt correct, theoretically. But the development of physics has shown that at any given moment, out of all conceivable constructions, a single one has always proved itself decidedly superior to all the rest. Nobody who has really gone deeply into the matter will deny that in practice the world of phenomena uniquely determines the theoretical system, in spite of the fact that there is no logical bridge between phenomena and their theoretical principles; this is what Leibnitz described so happily as a "pre-established harmony." Physicists often accuse epistemologists of not paying sufficient attention to this fact. Here, it seems to me, lie the roots of the controversy carried on some years ago between Mach and Planck.

       The longing to behold this pre-established harmony is the source of the inexhaustible patience and perseverance with which Planck has devoted himself, as we see, to the most general problems of our science, refusing to let himself be diverted to more grateful and more easily attained ends. I have often heard colleagues try to attribute this attitude of his to extraordinary will-power and discipline -- wrongly, in my opinion. The state of mind which enables a man to do work of this kind is akin to that of the religious worshiper or the lover; the daily effort comes from no deliberate intention or program, but straight from the heart. There he sits, our beloved Planck, and smiles inside himself at my childish playing-about with the lantern of Diogenes. Our affection for him needs no threadbare explanation. May the love of science continue to illumine his path in the future and lead him to the solution of the most important problem in present-day physics, which he has himself posed and done so much to solve. May he succeed in uniting quantum theory with electrodynamics and mechanics in a single logical system.