【诺奖得主Wilczek科普专栏】可能性和真理
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Frank Wilczek
想象世间万物可能或应该如何运作，可以帮助我们揭示真实的规律，反之亦然。
18世纪的哲学家戴维·休谟（David Hume）有一个论断：不可能用逻辑的方法从“是什么”推论出“应该是什么”，反之亦然。休谟的论证非常有力，通过区分“事实”与“价值判断”，对科学的范畴与法律、道德的范畴做了清晰的划分，这被哲学家戏称为“休谟的断头台”。
Envisioning how things could,and even should work in the universe can help to figure out how they do work-and vice versa.
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.
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