弗里曼·戴森 譯/肖明波

Not included in either of the two books is a paper written by Frank two years ago with the title “My father and I”. This is a tribute to his father， who was a professor of mathematics and died in 1973. It is a wonderfully sensitive account of his relationship to his father and of the pain that each of them suffered as a result of their separation. His father stayed in China through the hard years while Frank grew to greatness in America. Luckily， Frank was able to visit China twice before his father died and to sit by his bedside during his last illness.

The memoir “My father and I” ends on a happier note. It ends with a glorious moment of reunion. Frank describes how he stood at midnight on July 1， 1997， at the Hong Kong Convention and Exhibition Center， to watch the Union Jack being lowered and the flag of the People’s Republic being slowly raised， while the band played “Arise， you who would not be enslaved”. Frank writes， “Had father observed this historical ceremony marking the renaissance of the Chinese people， he would have been even more moved than I. ...The intellectuals of his generation had to personally experience the humiliating exploitations in the Foreign Concessions... and countless other rampant foreign oppressions.... How they had looked forward to the day when a prosperous China could stand up， when the British Empire had to lower the Union Jack and withdraw troops， when they can see for themselves the Chinese flag proudly announce to the world： This is Chinese Territory！ That day， July the first， 1997， is the day their generation had dreamed of throughout their lives”.

We can all rejoice that Frank was standing there to give his blessing and his father’s blessing to the reunion. For me， that pride and that feeling of fulfillment that Frank expresses have a special resonance. I too belong to a great and ancient civilization. My home-town in England was also the home-town of Alfred the scholar king， who made our town into a great center of learning eleven hundred years ago， while the Tang dynasty was establishing the system of government by scholars that endured for a thousand years in China. Our king Alfred was translating scholarly texts from Latin into English， soon after the Tang poet Tu Fu wrote the poem that Frank quotes at the beginning of his selected papers： “A piece of literature is meant for the millennium. But its ups and downs are known already in the author’s heart”.

Like Frank， I too left my homeland and became an American citizen. I still remember the humiliation of that day in Trenton2 when I took the oath of allegiance to the United States， and the ignoramus who performed the ceremony congratulated me for having escaped from the land of slavery to the land of freedom. With great difficulty I restrained myself from shouting out loud that my ancestors freed our slaves long before his ancestors freed theirs. I share Frank’s ambivalent feelings toward the United States， this country that has treated us both with so much generosity and has treated our ancient civilizations with so little understanding. And I share Frank’s pride in the peaceful lowering of the Union Jack and raising of the Chinese flag that he witnessed in Hong Kong， the place where our two ancient civilizations briefly came together and gave birth to something new.

Five years ago， I had the honor of speaking at the ceremony in Philadelphia， when the Franklin Medal was awarded to Frank Yang by the American Philosophical Society. We were assembled in the historic meeting-room of the society， with the portraits of Benjamin Franklin， the founder of the society， and Thomas Jefferson， one of its most active members， looking down at us. It was self-evident that Franklin and Jefferson approved of the award. We know that Frank Yang feels a special admiration for Franklin， since he gave the name of Franklin to his elder son. I would like to end this little talk with the same words that I used to praise Frank on that happy occasion.

Professor Yang is， after Einstein and Dirac， the preeminent stylist of twentieth-century physics. From his early days as a student in China to his later years as the sage of Stony Brook， he has always been guided in his thinking by a love of exact analysis and formal mathematical beauty. This love led him to his most profound and original contribution to physics， the discovery with Robert Mills of non-Abelian gauge fields. With the passage of time， his discovery of non-Abelian gauge fields is gradually emerging as a greater and more important event than the spectacular discovery of parity non-conservation which earned him the Nobel Prize. The discovery of parity non-conservation， the discovery that left-handed and right-handed gloves do not behave in all respects symmetrically， was a brilliant act of demolition， a breaking-down of intellectual barriers that had stood in the way of progress. In contrast， the discovery of non-Abelian gauge fields was a laying of foundations for new intellectual structures that have taken thirty years to build. The nature of matter as described in modern theories and confirmed by modern experiments is a soup of non-Abelian gauge fields， held together by the mathematical symmetries that Yang first conjectured forty-five years ago.

In science， as in urban renewal and international politics， it is easier to demolish old structures than to build enduring new ones. Revolutionary leaders may be divided into two kinds， those like Robespierre and Lenin who demolished more than they built， and those like Benjamin Franklin and George Washington who built more than they demolished. There is no doubt that Yang belongs to the second kind of revolutionary. He is a conservative revolutionary. Like his fellow-revolutionaries Franklin and Washington， he cherishes the past and demolishes as little as possible. He cherishes with equal reverence the great intellectual traditions of Western science and the great cultural traditions of his ancestors in China.

Yang likes to quote the words of Einstein， “The creative principle lies in mathematics. In a certain sense， therefore， I hold it true that pure thought can grasp reality， as the ancients dreamed”. On another occasion Yang said， “That taste and style have so much to do with one’s contribution in physics may sound strange at first， since physics is supposed to deal objectively with the physical universe. But the physical universe has structure， and one’s perceptions of this structure， one’s partiality to some of its characteristics and aversion to others， are precisely the elements that make up one’s taste. Thus it is not surprising that taste and style are so important in scientific research， as they are in literature， art and music”. Yang’s taste for mathematical beauty shines through3 all his work. It turns his least important calculations into miniature works of art， and turns his deeper speculations into masterpieces. It enables him， as it enabled Einstein and Dirac， to see a little further than other people into the mysterious workings of nature.

兩本書都沒有收錄的一篇文章，是弗蘭克兩年前寫的《父親和我》。這是他獻(xiàn)給自己父親——這位已在1973年去世的數(shù)學(xué)教授的一份厚禮。它對(duì)他們父子的關(guān)系以及分離給兩人帶來的痛苦作了精彩細(xì)膩的描述。在那段艱難歲月里，他父親一直留在中國，而弗蘭克卻在美國成名成家了。幸運(yùn)的是，弗蘭克得以在父親去世前兩度訪問中國，并在他臨終前陪在他的病床邊。

《父親和我》這篇回憶錄有一個(gè)較喜慶的結(jié)尾。它以一個(gè)美好的團(tuán)圓時(shí)刻結(jié)束了全文。弗蘭克描述了他在1997年7月1日零點(diǎn)時(shí)分，是如何站在香港會(huì)展中心，觀看英國國旗降下、中國國旗緩緩升起，聽著樂隊(duì)奏起“起來，不愿做奴隸的人們”。弗蘭克寫道：“要是父親能目睹這個(gè)象征中華民族復(fù)興的歷史性儀式，他一定會(huì)比我還要激動(dòng)?！麄兡且惠呏R(shí)分子親身經(jīng)歷了在租界中令人屈辱的欺凌……還有外族其他數(shù)不清的殘暴壓迫……他們多么盼望看到富強(qiáng)的祖國站起來的那一天，看到大英帝國降下國旗、撤出軍隊(duì)，看到中國的國旗向世界驕傲地宣示：這是中國的領(lǐng)土！這一天——1997年7月1日，正是他們終生夢(mèng)寐以求的一天?！?/p>

我們都很高興，弗蘭克當(dāng)時(shí)站在那里，送出了自己以及他父親對(duì)香港回歸的祝福。弗蘭克所表達(dá)的自豪和滿足感，特別能引起我的共鳴，因?yàn)槲乙矊儆谝粋€(gè)偉大而古老的文明。我在英國的故鄉(xiāng)，是學(xué)者艾爾弗雷德大帝的故鄉(xiāng)。他在1100年前將我的故鄉(xiāng)變成了一個(gè)偉大的學(xué)術(shù)中心，而與他同時(shí)代的唐朝，則在中國建立了持續(xù)千年的文官治理體制。我們的艾爾弗雷德大帝將拉丁文典籍譯成了英文，而此前不久，唐朝詩人杜甫寫出了“文章千古事，得失寸心知”——弗蘭克在他那本論文選集的前面就引用了這句詩。

和弗蘭克一樣，我也離開故土，成了一名美國公民。我仍記得我宣誓效忠美國那天，在特倫頓受到的羞辱：那位主持儀式的無知者祝賀我脫離奴役之鄉(xiāng)，加入自由之邦。我拼命克制才沒有沖他大聲喊出：我的祖輩遠(yuǎn)在他的祖輩解放他們的奴隸之前，就解放了我們的奴隸！我和弗蘭克一樣，對(duì)美國懷有矛盾的感情——這個(gè)國家對(duì)我們兩人都是如此慷慨，可是對(duì)我們古老的文明又了解得如此之少。我能體會(huì)弗蘭克在香港親眼目睹英國國旗和平降下、中國國旗冉冉升起時(shí)發(fā)自內(nèi)心的自豪。香港是我們這兩種古老文明經(jīng)過短暫的交匯，催生出嶄新事物的地方。

五年前，美國哲學(xué)學(xué)會(huì)在費(fèi)城舉行頒獎(jiǎng)儀式，授予弗蘭克·楊富蘭克林獎(jiǎng)?wù)?，我有幸在儀式上致辭。我們聚集在該學(xué)會(huì)那具有歷史意義的會(huì)議廳中，廳堂上方懸掛著學(xué)會(huì)創(chuàng)始人本杰明·富蘭克林和最活躍的一名會(huì)員托馬斯·杰斐遜畫像。毋庸多言，富蘭克林和杰斐遜都會(huì)贊同將這個(gè)獎(jiǎng)授予弗蘭克的。我們知道弗蘭克·楊特別欽佩富蘭克林，他甚至給自己的長子取名為富蘭克林。我想借用我在那個(gè)歡樂場合稱頌弗蘭克的話，來結(jié)束今天這個(gè)簡短的演講。

楊教授是繼愛因斯坦和狄拉克之后有如設(shè)計(jì)師一般的杰出物理學(xué)家。從他早年在中國當(dāng)學(xué)生時(shí)開始，直到后來成為紐約州立大學(xué)石溪分校的哲人，引導(dǎo)他的思考的，一直是他對(duì)精確分析和數(shù)學(xué)形式美的熱愛。這種熱愛使他做出了對(duì)物理學(xué)影響最深遠(yuǎn)的和最有創(chuàng)見的貢獻(xiàn)——跟羅伯特·米爾斯一道發(fā)現(xiàn)的非阿貝爾規(guī)范場。隨著時(shí)間的推移，他所發(fā)現(xiàn)的非阿貝爾規(guī)范場，已漸漸成為比宇稱不守恒這個(gè)驚人的發(fā)現(xiàn)更重大的貢獻(xiàn)，雖然是后者使他獲得了諾貝爾獎(jiǎng)。對(duì)宇稱不守恒的發(fā)現(xiàn)，即對(duì)左右手手套并非在各個(gè)方面都表現(xiàn)出對(duì)稱性的發(fā)現(xiàn)，是一項(xiàng)了不起的破除行動(dòng)，它清除了前進(jìn)道路上的思維障礙。與此相反，非阿貝爾規(guī)范場的發(fā)現(xiàn)則為后來經(jīng)過30年才建立起來的新思維結(jié)構(gòu)奠定了基礎(chǔ)。由當(dāng)代理論描述并為當(dāng)代實(shí)驗(yàn)所證實(shí)的物質(zhì)的本質(zhì)，是多個(gè)非阿貝爾規(guī)范場的一種混疊，將它們合在一起的是數(shù)學(xué)對(duì)稱性，楊在45年前率先作出了這一猜想。

科學(xué)研究也像在城市重建和國際政治中一樣，破過時(shí)的舊總比立持久的新更容易。革命領(lǐng)袖可以分為兩類：一類是羅伯斯庇爾和列寧那種，破壞的比創(chuàng)建的多;另一類是本杰明·富蘭克林和喬治·華盛頓那種，創(chuàng)建的比破壞的多。毫無疑問，楊是屬于后一類的革命者。他是一位保守的革命者。跟富蘭克林和華盛頓一樣，他珍惜過去，盡可能少去破壞它。對(duì)西方科學(xué)的偉大學(xué)術(shù)傳統(tǒng)和中國祖先的偉大文化傳統(tǒng)，他懷著同樣崇敬的心情予以珍惜。

楊喜歡引用愛因斯坦這段話：“創(chuàng)造的源泉在于數(shù)學(xué)。因此，在某種意義上，我相信，像古人夢(mèng)想的那樣，純粹通過思考可以把握事物的真相。”在另一個(gè)場合，楊教授說過：“一個(gè)人的品位和風(fēng)格竟與他對(duì)物理學(xué)的貢獻(xiàn)有如此密切的關(guān)系，乍聽起來也許會(huì)令人感到奇怪，因?yàn)槲锢韺W(xué)被認(rèn)為是一門客觀地研究物質(zhì)世界的學(xué)問。然而，物質(zhì)世界具有結(jié)構(gòu)，而一個(gè)人對(duì)這些結(jié)構(gòu)的洞察，對(duì)這些結(jié)構(gòu)中某些特點(diǎn)的好惡，正是構(gòu)成其自有風(fēng)格的要素。因此，品位和風(fēng)格之于科學(xué)研究，就像它們對(duì)文學(xué)、藝術(shù)和音樂一樣重要，這是不足為奇的?！睏钤跀?shù)學(xué)美方面的品位體現(xiàn)在他所有的工作中。它使他最不重要的計(jì)算變成了袖珍的藝術(shù)品，又使得他深層次的猜想成為杰作。這種品位還使他能夠?qū)Υ笞匀坏纳衩剡\(yùn)作看得比別人更深遠(yuǎn)一點(diǎn)，曾經(jīng)愛因斯坦和狄拉克也是如此。