Imagine you're watching a runaway trolley barreling down the tracks straight towards five workers who can't escape.
想象你眼前有一辆失控的电车，飞速冲下轨道，轨道前方有5个工人，难逃此劫。
You happen to be standing next to a switch that will divert the trolley onto a second track.
而你正巧站在道岔旁边，可以将电车引向另一条轨道上。
Here's the problem. That track has a worker on it, too, but just one.
那么，问题来了。另一条轨道上面也有工人，但是只有一个。
What do you do? Do you sacrifice one person to save five?
这时候，你会怎么办？你会选择牺牲一个人来挽救五个人吗？
This is the trolley problem, a version of an ethical dilemma that philosopher Philippa Foot devised in 1967.
这就是我们所说的电车难题，是由哲学家菲利帕·福特在1967年提出的道德困境问题。
It's popular because it forces us to think about how to choose when there are no good choices.
这个问题能引起大家的兴趣是因为它促使我们思考如何在困境之中做出抉择。
Do we pick the action with the best outcome or stick to a moral code that prohibits causing someone's death?
我们应该选择一个最好的结果，还是坚守不做出任何伤害他人生命的行为道德准则？
In one survey, about 90% of respondents said that it's okay to flip the switch,
一项调查显示，大约90%的参与者选择搬动道岔，
letting one worker die to save five, and other studies,
牺牲一人来拯救五个人的生命，其他试验，
including a virtual reality simulation of the dilemma, have found similar results.
包括一个虚拟现实模拟研究也得出了相似的结果。
These judgments are consistent with the philosophical principle of utilitarianism
这与功利主义的观点相吻合，
which argues that the morally correct decision is the one that maximizes well-being for the greatest number of people.
即认为道德上正确的决定是依据为最多的人提供最大的利益这一原则做出的。
The five lives outweigh one, even if achieving that outcome requires condemning someone to death.
五个人的生命总归大于一个人的生命，即便是以牺牲一个人的生命为代价。
But people don't always take the utilitarian view, which we can see by changing the trolley problem a bit.
然而人们并不都遵循功利主义的思想，我们从电车难题的变式中就可以发现。
This time, you're standing on a bridge over the track as the runaway trolley approaches.
这一次，你站在天桥上，一辆失控的电车正朝你驶来。
Now there's no second track, but there is a very large man on the bridge next to you.
此时并没有第二条轨道，但是你的旁边站着一位体型庞大的男人。
If you push him over, his body will stop the trolley, saving the five workers, but he'll die.
如果你把他推下天桥，他的身体能够让电车停下来，拯救五个人的性命，但是那个男人会牺牲。
To utilitarians, the decision is exactly the same, lose one life to save five.
对于功利主义者而言，这一次选择与上一次相同，牺牲一个人来拯救另五个人。
But in this case, only about 10% of people say that it's OK to throw the man onto the tracks.
但是在这次试验中，只有大约10%的参与者认为可以把那个男人推落到轨道上。
Our instincts tell us that deliberately causing someone's death is different than allowing them to die as collateral damage.
直觉告诉我们，故意造成他人死亡的行为不同于间接伤害造成死亡。

It just feels wrong for reasons that are hard to explain.
这属于人之常情，其背后的原因很难解释清楚。
This intersection between ethics and psychology is what's so interesting about the trolley problem.
正是道德伦理与心理学产生的交集让电车难题变得非常有意思。
The dilemma in its many variations reveal that what we think is right or wrong depends on factors
电车难题及其多种变式揭示了我们在做出道德判断时依赖于多种因素，
other than a logical weighing of the pros and cons.
而非仅仅通过合乎逻辑的利弊权衡。
For example, men are more likely than women to say it's okay to push the man over the bridge.
比如说，男性比女性更有可能选择把那个男人推下天桥。
So are people who watch a comedy clip before doing the thought experiment.
参加试验之前看了喜剧片的人，也更可能做出同样的选择。
And in one virtual reality study, people were more willing to sacrifice men than women.
一项虚拟现实研究发现，相较女性，人们更愿意选择牺牲男性。
Researchers have studied the brain activity of people thinking through the classic and bridge versions.
研究人员在探究原始电车难题及其变式情形下人们的脑部活动时发现，
Both scenarios activate areas of the brain involved in conscious decision-making and emotional responses.
两种情景都激发了脑部负责有意识决策和情绪反应的部位。
But in the bridge version, the emotional response is much stronger.
但是在变式情况中，参与者的情绪反应更加激烈。
So is activity in an area of the brain associated with processing internal conflict.
脑部负责处理内部冲突的部位也更加活跃。
Why the difference? One explanation is that pushing someone to their death feels more personal,
为什么会产生这些变化？一种解释是，把人推下桥致死对个人的冲击更大，
activating an emotional aversion to killing another person,
激发了对于杀人行为的厌恶之情，
but we feel conflicted because we know it's still the logical choice.
但是我们又很矛盾，因为我们知道这是符合逻辑的选择。
"Trolleyology" has been criticized by some philosophers and psychologists.
一些哲学家和心理学家对电车难题持批评态度。
They argue that it doesn't reveal anything because its premise is so unrealistic that study participants don't take it seriously.
他们认为这并没有揭示任何东西，因为问题发生的前提非常不现实，以致于试验参与者并不会认真对待。
But new technology is making this kind of ethical analysis more important than ever.
然而，新科技正让这种道德分析变得比以往更加重要。
For example, driver-less cars may have to handle choices like causing a small accident to prevent a larger one.
比如说，无人驾驶的汽车可能会面临造成小事故来避免大事故的选择。
Meanwhile, governments are researching autonomous military drones
同时，政府在研发军用无人机
that could wind up making decisions of whether they'll risk civilian casualties to attack a high-value target.
最终能够做出牺牲平民生命以攻击高价值目标的决定。
If we want these actions to be ethical, we have to decide in advance how to value human life and judge the greater good.
如果我们希望这样的行为变得合乎道德，那么我们必须首先决定如何衡量人类生命的价值，并评判什么是符合多数人利益的。
So researchers who study autonomous systems are collaborating with philosophers
那么，独立系统的研究人员应该和哲学家一起，
to address the complex problem of programming ethics into machines,
处理机器编程过程中遇到的道德难题，
which goes to show that even hypothetical dilemmas can wind up on a collision course with the real world.
而这正恰恰说明了假设中的困境，最终也会与现实世界发生碰撞。