Imagine as a thought experiment that you live in a small village and depend on the local fish pond for food.
有这样一道思考题，假设你住在一个小村庄里，村民们依靠在当地鱼塘打渔为食。
You share the pond with three other villagers.
你要与另外三位村民共享这个鱼塘。
The pond starts off with a dozen fish, and the fish reproduce.
鱼塘自起始时有十二条鱼，同时鱼也会繁殖。
For every two fish, there will be one baby added each night.
每两条鱼每晚会产出一条小鱼。
So, in order to maximize your supply of food, how many fish should you catch each day?
那么为了最大化你们的食物供给，你们每天可以捕多少条鱼呢？
Take a moment to think about it.
让我们花点时间思考一下。
Assume baby fish grow to full size immediately and that the pond begins at full capacity,
假设大鱼每晚产下的小鱼在次日就会变为大鱼，鱼塘自起始时也有足够的条件供鱼类生息，
and ignore factors like the sex of the fish you catch.
同时忽略鱼的性别以及类似的影响因素。
The answer? One, and it's not just you.
答案是？一条鱼，而且不仅仅是你只能打一条鱼。
The best way to maximize every villager's food supply is for each fisherman to take just one fish each day.
最大化每位村民食物供给的方法就是，每位渔民每天只能捕一条鱼。
Here's how the math works. If each villager takes one fish, there will be eight fish left over night.
算法是这样的。如果每位村民每天打一条鱼，当晚鱼塘内会剩下八条鱼。
Each pair of fish produces one baby, and the next day, the pond will be fully restocked with twelve fish.
每两条鱼会繁殖出一条小鱼，于是次日，鱼塘内鱼的数量又会恢复到十二条。
If anyone takes more than one, the number of reproductive pairs drops, and the population won't be able to bounce back.
如果有任何一位多捕了一条，鱼塘内的繁殖对数量就会减少，鱼的数量也就无法恢复。
Eventually, the fish in the lake will be gone, leaving all four villagers to starve.
最终鱼塘里也就不再有鱼了，而村民们只能挨饿。
This fish pond is just one example of a classic problem called the tragedy of the commons.
这个鱼塘引发的问题，只是这类问题的一个示例，即所谓的“公用品悲剧”。
The phenomenon was first described in a pamphlet by economist William Forster Lloyd in 1833
这个现象首次于1833年由威廉·福斯特·洛伊提出，发布在一本小手册上，
in a discussion of the overgrazing of cattle on village common areas.
以此讨论了在村庄的公共区域内过度放牧的现象。
More than 100 years later, ecologist Garrett Hardin revived the concept
一百多年后，经济学家加勒特·哈丁再次提出了这个概念，
to describe what happens when many individuals all share a limited resource,
用来描述当许多人共享一种有限的资源时会发生什么，
like grazing land, fishing areas, living space, even clean air.
比如共用牧场、鱼塘、生活空间，甚至是清新的空气。

Hardin argued that these situations pit short-term self-interest against the common good, and they end badly for everyone,
哈丁认为造成这些公共资源短缺的现象是由于人们盲目追求短期自我利益，而这最终只会有害于所有人，
resulting in overgrazing, overfishing, overpopulation, pollution, and other social and environmental problems.
导致过度放牧、过度捕鱼、人口过剩、大气污染以及其他社会环境问题。
The key feature of a tragedy of the commons is that it provides an opportunity for an individual to benefit him or herself
“公用品悲剧”的主要特点是，它为人们提供了让自己获益的机会，
while spreading out any negative effects across the larger population.
同时却对大众造成负面影响。
To see what that means, let's revisit our fish pond.
想要进一步了解它的含义，让我们回到之前的鱼塘思考题。
Each individual fisherman is motivated to take as many fish as he can for himself.
每位渔民都有理由为自己捕捞尽可能多的鱼。
Meanwhile, any decline in fish reproduction is shared by the entire village.
然而同时鱼塘内鱼的繁殖量下降是需要所有村民一起承受的。
Anxious to avoid losing out to his neighbors,
急于避免自己的捕鱼量比邻居少，
a fisherman will conclude that it's in his best interest to take an extra fish, or two, or three.
渔民会为了个人利益尽可能地多捕一条鱼，或者两条，或者三条。
Unfortunately, this is the same conclusion reached by the other fisherman, and that's the tragedy.
不幸的是，每位渔民都是这样想的，而这就是悲剧的开始。
Optimizing for the self in the short term isn't optimal for anyone in the long term.
自身短期的利益往往与群体长期利益向冲突。
That's a simplified example, but the tragedy of the commons plays out in the more complex systems of real life, too.
以上只是一个简单的例子，然而公用品悲剧也发生在现实生活中更复杂的情形里。
The overuse of antibiotics has led to short-term gains in livestock production and in treating common illnesses,
过多使用抗生素可以增长畜牧生产的短期收益，并治疗一些人类普遍的疾病，
but it's also resulted in the evolution of antibiotic-resistant bacteria, which threaten the entire population.
但同时也会引发细菌的抗药性，从而对整个人口系统造成威胁。
A coal-fired power plant produces cheap electricity for its customers and profits for its owners.
依靠燃煤发电可以为人们提供廉价的电力并使发电厂获利。
These local benefits are helpful in the short term,
这些诚然可以为当地发展提供短期的利益，
but pollution from mining and burning coal is spread across the entire atmosphere and sticks around for thousands of years.
但采矿和燃煤造成的污染则会遍布整个大气层，在几千年内都无法消失。
There are other examples, too.
这样的例子举不胜举。
Littering, water shortages, deforestation, traffic jams, even the purchase of bottled water.
乱扔垃圾、水资源短缺、砍伐森林、交通堵塞，甚至是购买瓶装水。
But human civilization has proven it's capable of doing something remarkable.
然而人类文明已经证明了它可以做一些卓尔不群的事。
We form social contracts, we make communal agreements, we elect governments, and we pass laws.
我们起草社会契约、我们制定公用协定、我们选择政府党派、我们通过法律议案。
All this to save our collective selves from our own individual impulses.
这都是为了拯救因个人行为而受损的集体利益。
It isn't easy, and we certainly don't get it right nearly all of the time.
这并不是简单的事，而我们也没有经常做对。
But humans at our best have shown that we can solve these problems
但当人类怀有最好的意愿时，我们总是可以解决这些问题，
and we can continue to do so if we remember Hardin's lesson.
如果我们能铭记哈丁的这个理论，就能继续做正确的决定。
When the tragedy of the commons applies, what's good for all of us is good for each of us.
当公用品的利益出现时，对大家都有益的才是对每个人有益的。