大師走好 回顧約翰納什的美麗人生

John Nash, a Nobel laureate and mathematical genius whose struggle with mental illness was documented in the Oscar-winning film “A Beautiful Mind”, was killed in a car accident on Saturday. He was 86. The accident, which occurred when the taxi Nash was traveling in collided with another car on the New Jersey Turnpike, also claimed the life of his 82-year-old wife, Alicia. Neither of the two drivers involved in the accident sustained life-threatening injuries.

上週六，奧斯卡獲獎影片《美麗心靈》主人公的原型、美國數學天才、諾貝爾獎得主約翰•納什遭遇車禍去世，終年86歲。事故發生時，納什夫婦乘坐的一輛出租車在新澤西高速路上與另外一輛汽車相撞，納什82歲的妻子艾麗西亞也在車禍中遇難。出租車司機以及對方車輛的司機都沒有遭受致命傷。

Born in West Virginia in 1928, Nash displayed an acuity for mathematics early in life, independently proving Fermat’s little theorem before graduating from high school. By the time he turned 30 in 1958, he was a bona fide academic celebrity. At Princeton, Nash published a 27-page thesis that upended the field of game theory and led to applications in economics, international politics, and evolutionary biology. His signature solution—known as a “Nash Equilibrium”—found that competition among two opponents is not necessarily governed by zero-sum logic. Two opponents can, for instance, each achieve their maximum objectives through cooperating with the other, or gain nothing at all by refusing to cooperate. This intuitive, deceptively simple understanding is now regarded as one of the most important social science ideas in the 20th century, and a testament to his almost singular intellectual gifts.

1928年，納什出生在美國西佛吉尼亞州。他很早就表現出出色的數學天賦，高中還未畢業就已經獨立證明了費馬小定理。1958年，而立之年的納什已是名副其實的學術界名人。在普林斯頓，納什一篇27頁的論文顛覆了博弈論領域，博弈論此後被廣泛應用於經濟學、國際政治以及進化生物學領域。著名的解決方案“納什均衡”就是由他發現並以他的名字命名。“納什均衡”指博弈雙方不一定受到零和邏輯的約束，比如，博弈雙方可以通過合作均取得最大收益，或者不合作承擔零收益（但也沒有損失）。這表面看來似乎很好理解的理論卻已經成爲20世紀最重要的社會學觀點之一，而這也是納什卓越智慧的明證。

But in the late 1950s, Nash began a slide into mental illness—later diagnosed as schizophrenia—that would cost him his marriage, derail his career, and plague him with powerful delusions. Nash believed at various times that he was the biblical figure Job, a Japanese shogun, and a “messianic figure of great but secret importance.” He obsessed with numbers and believed The New York Times published coded messages from extraterrestrials that only he could read.

但是，自1950年代末，納什開始受到精神疾病的折磨，經診斷他患上了精神分裂症。他因此離婚，事業毀於一旦，他自己也飽受幻覺的折磨。他時而以爲自己是聖經中的約伯，時而把自己當做日本古代的將軍，時而又以爲自己是“隱祕而偉大的救世主”。他沉溺於數字之中，堅信《紐約時報》中藏匿着外星人留下的密碼，而只有他才能解開。

Mental institutions and electroshock therapy failed to cure him, and for much of the next three decades, Nash wandered freely on the Princeton campus, scribbling idly on empty blackboards and staring blankly ahead in the library. Atlantic contributor Robert Wright, an undergraduate at Princeton in the late 1970s, remembers Nash as “some math genius that went crazy” who wore colorful sneakers and quietly watched people. His schizophrenia removed him completely from his work. By the time Nash was awarded the Nobel prize in Economics in 1994 (along with John Harsanyi and Reinhard Selten), he hadn’t published a paper in 36 years.

精神病院、電擊療法都沒能治癒納什。在隨後的三十年間，他遊蕩在普林斯頓的校園裏，或在空黑板上“塗鴉”，或在圖書館中發呆。《大西洋月刊》撰稿人羅伯特•賴特是普林斯頓1970年代的畢業生，他回憶到：這位“瘋了的數學天才”總是穿着彩色的運動鞋，安靜地看着人來人往。精神分裂讓他完全無法工作，直至1994年（與約翰•海薩尼 、萊因哈德•澤爾騰共同）獲得諾貝爾經濟學獎的36年間，納什再無論文發表。

But like a child cured of a nightmare by the switch of a light, Nash recovered from his illness seemingly by choosing not to be sick anymore. “I emerged from irrational thinking, ultimately, without medicine other than the natural hormonal changes of aging,” he wrote in 1996. Five years later, the release of the film A Beautiful Mind, based on Sylvia Nasar’s 1998 book of the same name, amplified Nash’s extraordinary life story to an international audience. He continued to work, travel, and speak at conferences for the rest of his life.

就像打開燈就能讓孩子走出夢魘一般，決定不再做病人後納什似乎就自己擺脫了病魔。1996年，他寫到：“最終，我擺脫了妄想，不是依靠藥物，而是隨着年紀見長體內激素自然而然發生了變化。”5年後，根據1998年西爾維婭•娜薩同名小說改編的電影《美麗心靈》上映，納什與衆不同的故事爲全世界觀衆所知。而故事的主人公在接下來的人生中依舊繼續工作、旅行、在大大小小的會議上發言。

It’s tempting to wonder what Nash might have accomplished had mental illness not robbed him of so many productive years. But the “beautiful mind” that gave him such prodigious mathematical talent was indivisible from the one which spawned powerful delusions. In her study of creativity published in the July/August 2014 edition of the Atlantic, Nancy Andreasen related a memorable anecdote from Nasar’s book. Upon visiting Nash at a mental institution, a colleague asked how a man so devoted to reason and logical truth could believe that extraterrestrials were sending him messages.

人們也許不禁想問，如果沒有這麼多年精神疾病的困擾，納什又將取得怎樣的成就？他的美麗心靈既帶給了他巨大的數學成就，同時也讓他飽受幻覺的折磨。《大西洋月刊》7/8月刊中，南希•安卓森關於創造力的一篇文章就提到了娜薩書中一個令人難忘的故事：納什的一個同事去精神病院看望他時，曾問他，身爲一個如此執着於理性與邏輯真理的人，他爲何會相信外星人傳遞信息這種事。

“Because the ideas I had about supernatural beings came to me the same way that my mathematical ideas did,” replied Nash. “So I took them seriously.”

納什答道：“因爲那些關於超自然生物的想法向我襲來，就彷彿曾經的那些數學觀點一樣。於是，我當真了。”