諾獎得主Wilczek：可能性和真理_風聞
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撰文 | Frank Wilczek
翻譯 | 胡風、梁丁當
中文版
18世紀的哲學家戴維·休謨（David Hume）有一個論斷：不可能用邏輯的方法從“是什麼”推論出“應該是什麼”，反之亦然。休謨的論證非常有力，通過區分“事實”與“價值判斷”，對科學的範疇與法律、道德的範疇做了清晰的劃分，這被哲學家戲稱為“休謨的斷頭台”。
但是邏輯並非一切。為了睿智地思考我們應該做什麼，需要先設想未來可能會發生什麼，這樣我們才能採取相應的行動。這意味着我們需要思考未來，一個充滿諸多可能性的未來。
著名的哲學家兼棒球捕手尤吉·貝拉（Yogi Berra）有句名言 ：“很難做出預測，尤其是對未來的預測。”尤吉和物理學家可謂是靈犀相通。根據現代物理學，由於相互作用帶來的複雜性，再加上量子力學和混沌理論的限制，我們根本無法明確地預測將來。但是，我們可以想象未來的可能性。正是在這個意義上，愛因斯坦説 ：“想象力比知識更重要”，因為想象力“涵蓋了無限的可能性。”
當我們引入“未來的可能性”這個新的維度，就能夠繞開休謨的斷頭台，構建出一個迷人的三角形。它的三個角分別對應着“是什麼”、“可能是什麼”和“應該是什麼”。有四個箭頭將它們連接起來。
第一個箭頭從“是什麼”指向“可能是什麼”。科學的主旨是回答“是什麼”。但科學發展到今天，不僅讓我們對物質、生命與信息是什麼有了深入的理解，也指引了未來可能的方向。從這個角度來説，赫伯特·威爾斯（H.G. Wells）、亞瑟·克拉克（Arthur C. Clarke）、奧克塔維亞·巴特勒（Octavia Butler）、石黑一雄（Kazuo Ishiguro）等人的科幻文學，通過構想未來的世界，對通常來説更加理性化的科研論文作了生動的補充。
第二個箭頭從“可能是什麼”指向“應該是什麼”。這種聯繫不能通過邏輯或使用通常的科學方法建立。但是，通過想象未來的各種可能性，我們可以對它們進行理智的比較和分析，從中篩選出那些我們所期望的，避免那些我們所不希望出現的。雖然不同的人選擇也可能不同，但建立在想象力基礎上的相互理解有助於提升討論的質量。
有兩個不同的箭頭從“應該是什麼”指回“是什麼”。第一個很容易理解 ：你必須知道想去哪裏，才能到達那裏。除此之外，還有另一支美麗而神秘的箭頭 ：想象這個世界應該是怎樣的，可以幫助我們猜測它可能的運行方式。不可思議的是，這竟然可以指引我們通往真理。
近代基礎物理學和宇宙學的發展都呈現出這個特徵。尤金·維格納（Eugene Wigner）談論着“數學在自然科學中的不合理有效性”。保羅·狄拉克（Paul Dirac）則寫到 ：“如果一個人追求優美的數學表達，而他剛好有好的洞察力，那麼他就必然會取得進展。”
這些洞見來自他們各自的經驗。羣論發展於19世紀末，在維格納把它引入原子的量子力學理論中時，這個理論還很生僻。通過分析電子波函數的對稱性，維格納自然而然地揭示了元素週期表的本質。狄拉克好奇地將狹義相對論和量子理論融合，得到了一個優美的描述電子的數學方程。但這個方程似乎有個致命的缺陷。為了理解這個“缺陷”，狄拉克預言了一個奇妙的新世界 ：反物質。
更廣泛地講，通過想象宇宙世界應該有的模樣，愛因斯坦發展出了廣義相對論，量子物理學家發展出了基本力的現代理論，宇宙學家提出了極其簡單的大爆炸模型。簡而言之，對未來的無限想象指引着通向真實本身的路。
英文版
The 18th-century philosopher David Hume argued that it is impossible to proceed, by purely logical reasoning, from statements about what is to statements about what should be (or vice versa). Hume’s arguments were so forceful and convincing that philosophers still today speak of “Hume’s guillotine,” or the fact/value distinction, which separates the world of science from the world of law and morality.
But logic isn’t everything. To think intelligently about what we ought to do,we must think about what should happen, so that we can act to make it happen. In short, we need to think about futures. That’s futures, with an s. As the famous philosopher and bad-ball hitter Yogi Berra observed, “It’s tough to make predictions, especially about the future.” Here Yogi anticipated modern trends in quantum mechanics and chaos theory that put fundamental limits on predictability—as does the sheer complexity of the world, with its many interacting parts. But though we can’t predict the future, we can imagine possible futures. It was in this context that Albert Einstein asserted, “Imagination is more important than knowledge,” because imagination “embraces all there ever will be.”
Thinking about futures opens up a charmed triangle that loops around Hume’s guillotine. At the corners are the domains of is, could be and should be. They are linked by four arrows.
The first arrow points from what is to what could be. Science is primarily concerned with what is. But modern science has achieved such fundamental understanding of matter, life, and information that it also provides a solid pointer to what could be. Here, prophetic literature from H.G. Wells and Arthur C. Clarke to Octavia Butler and Kazuo Ishiguro supplements the (usually) more sober scientific literature.
A second arrow points from what could be to what should be. This connection cannot be drawn by logic, or by using normal scientific methods. But upon imagining alternative futures clearly we can compare them intelligently, chooseamong those that are desirable and avoid those that are undesirable. Of course, different people might make different choices, but imaginative understanding elevates the level of discussion.
Two different arrows point from what should be back around to what is. The first is easy to understand: You must know where you want to go in order to get there. But there is another arrow, beautiful and mysterious, pointing in the same direction. It is the remarkable fact, especially characteristic of recent fundamental physics and cosmology, that thinking about how the world should work can lead us to make guesses that turn out to describe how the world does work. Eugene Wigner spoke of “the unreasonable effectiveness of mathematics in the natural sciences,” and Paul Dirac wrote, “It seems that if one is working from the point of view of getting beauty in one’s equations, and if one has really sound insight, one is on a sure line of progress.”
They spoke from personal experience. Using (formerly) esoteric late 19th-century mathematics, Wigner showed how the periodic table of elements becomes evident within the quantum theory of atoms, once the wave functions of electrons are analyzed into symmetrical patterns. Dirac’s playful fusion of special relativity and quantum theory led him to a beautiful equation for electrons that seemed to have a fatal flaw. But the “flaw,” properly understood, predicted something wonderfully new: antimatter.
More generally, visions of how things should be guided Einstein to general relativity, quantum physicists to our present theories of the other fundamental forces, and cosmologists to their radically simple model of the big bang—in short, to the way things are.
Frank Wilczek
本文經授權轉載自微信公眾號“蔻享學術”，編輯：黃琦。
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