Justice: What's the Right Thing to Do?

Suppose you are the driver of a trolley car hurtling down the track at sixty miles an hour. Up ahead you see five workers standing on the track, tools in hand. You try to stop, but you can’t. The brakes don’t work. You feel desperate, because you know that if you crash into these five workers, they will all die. (Let’s assume you know that for sure.)

Suddenly, you notice a side track, off to the right. There is a worker on that track, too, but only one. You realize that you can turn the trolley car onto the side track, killing the one worker, but sparing the five.

What should you do? Most people would say, “Turn! Tragic though it is to kill one innocent person, it’s even worse to kill five.” Sacrificing one life in order to save five does seem the right thing to do.

Now consider another version of the trolley story. This time, you are not the driver but an onlooker, standing on a bridge overlooking the track. (This time, there is no side track.) Down the track comes a trolley, and at the end of the track are five workers. Once again, the brakes don’t work. The trolley is about to crash into the five workers. You feel helpless to avert this disaster—until you notice, standing next to you on the bridge, a very heavy man. You could push him off the bridge, onto the track, into the path of the oncoming trolley. He would die, but the five workers would be saved. (You consider jumping onto the track yourself, but realize you are too small to stop the trolley.)

Would pushing the heavy man onto the track be the right thing to do? Most people would say, “Of course not. It would be terribly wrong to push the man onto the track.”

Pushing someone off a bridge to a certain death does seem an awful thing to do, even if it saves five innocent lives. But this raises a moral puzzle: Why does the principle that seems right in the first case—sacrifice one life to save five—seem wrong in the second?

If, as our reaction to the first case suggests, numbers count—if it is better to save five lives than one—then why shouldn’t we apply this principle in the second case, and push? It does seem cruel to push a man to his death, even for a good cause. But is it any less cruel to kill a man by crashing into him with a trolley car?

Perhaps the reason it is wrong to push is that doing so uses the man on the bridge against his will. He didn’t choose to be involved, after all. He was just standing there.

But the same could be said of the person working on the side track. He didn’t choose to be involved, either. He was just doing his job, not volunteering to sacrifice his life in the event of a runaway trolley. It might be argued that railway workers willingly incur a risk that bystanders do not. But let’s assume that being willing to die in an emergency to save other people’s lives is not part of the job description, and that the worker has no more consented to give his life than the bystander on the bridge has consented to give his.

Maybe the moral difference lies not in the effect on the victims—both wind up dead—but in the intention of the person making the decision. As the driver of the trolley, you might defend your choice to divert the trolley by pointing out that you didn’t intend the death of the worker on the side track, foreseeable though it was; your purpose would still have been achieved if, by a great stroke of luck, the five workers were spared and the sixth also managed to survive.

But the same is true in the pushing case. The death of the man you push off the bridge is not essential to your purpose. All he needs to do is block the trolley; if he can do so and somehow survive, you would be delighted.

Or perhaps, on reflection, the two cases should be governed by the same principle. Both involve a deliberate choice to take the life of one innocent person in order to prevent an even greater loss of life. Perhaps your reluctance to push the man off the bridge is mere squeamishness, a hesitation you should overcome. Pushing a man to his death with your bare hands does seem more cruel than turning the steering wheel of a trolley. But doing the right thing is not always easy.

We can test this idea by altering the story slightly. Suppose you, as the onlooker, could cause the large man standing next to you to fall onto the track without pushing him; imagine he is standing on a trap door that you could open by turning a steering wheel. No pushing, same result. Would that make it the right thing to do? Or is it still morally worse than for you, as the trolley driver, to turn onto the side track?

It is not easy to explain the moral difference between these cases—why turning the trolley seems right, but pushing the man off the bridge seems wrong. But notice the pressure we feel to reason our way to a convincing distinction between them—and if we cannot, to reconsider our judgment about the right thing to do in each case. We sometimes think of moral reasoning as a way of persuading other people. But it is also a way of sorting out our own moral convictions, of figuring out what we believe and why.

Some moral dilemmas arise from conflicting moral principles. For example, one principle that comes into play in the trolley story says we should save as many lives as possible, but another says it is wrong to kill an innocent person, even for a good cause. Confronted with a situation in which saving a number of lives depends on killing an innocent person, we face a moral quandary. We must try to figure out which principle has greater weight, or is more appropriate under the circumstances.

Other moral dilemmas arise because we are uncertain how events will unfold. Hypothetical examples such as the trolley story remove the uncertainty that hangs over the choices we confront in real life. They assume we know for sure how many will die if we don’t turn—or don’t push. This makes such stories imperfect guides to action. But it also makes them useful devices for moral analysis. By setting aside contingencies—“What if the workers noticed the trolley and jumped aside in time?”—hypothetical examples help us to isolate the moral principles at stake and examine their force.

Michael J. Sandel
is the Anne T. and Robert M. Bass Professor of Government at Harvard University, where he has taught political philosophy since 1980. His books include What Money Can’t Buy: The Moral Limits of Markets, Liberalism and the Limits of Justice; Democracy’s Discontent; Public Philosophy: Essays on Morality in Politics; and Justice: What’s the Right Thing to Do? His undergraduate course “Justice” has enrolled more than 15,000 students, and was the first Harvard course to be made freely available online (www.JusticeHarvard.org) and on television.

This article is excerpted from Justice: What’s the Right Thing to Do? © Michael J. Sandel. Farrar, Straus and Giroux, New York: 2009. Reprinted with permission.

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