Debate: Would you kill one to save five?

Push the man

The two cases are morally the same. In both, one dies and five are saved. If you should pull the lever, you should push the man.

Best argument

What matters morally is outcomes: five lives are worth more than one. The difference in our reactions is a matter of psychology, not morality. Joshua Greene's brain-imaging research suggests that the footbridge case triggers strong emotional responses to up-close, personal violence, which evolved in small groups and may not track what is right. On reflection, we should trust the reasoning over the gut.

Strongest objection

This seems to license terrible acts whenever the numbers favour them, including killing a healthy patient to harvest organs for five others. Almost no one accepts that conclusion, so there must be something wrong with the reasoning.

The reply

Some consequentialists accept the hard cases; others argue that a policy of harvesting organs would destroy trust in medicine and so produce worse outcomes overall.

Defended by

Peter Singer, Joshua Greene, Jeremy Bentham

Means versus side effect

Diverting the trolley is permissible because the one person's death is a foreseen side effect. Pushing the man is wrong because his death is the means by which the five are saved.

Best argument

The doctrine of double effect, traced to Thomas Aquinas, holds that it can be permissible to bring about a harm as a side effect of pursuing a good end, when it would not be permissible to bring about the same harm as a means to that end. In the lever case, you would be glad if the one person somehow escaped. In the footbridge case, you need the man to be hit; his body is your tool.

Strongest objection

Thomson's loop case: the side track loops back to the main line, so the trolley would hit the five from behind if the one person were not there. Now the one person's body is a means of stopping the trolley. Yet many people still think it is permissible to pull the lever.

The reply

Defenders argue that intuitions about the loop are divided, and that the doctrine captures something real even if it needs refinement.

Defended by

Thomas Aquinas, Elizabeth Anscombe, Philippa Foot

Doing versus redirecting

It is permissible to redirect an existing threat toward fewer people, but not to create a new threat or use a person as a tool.

Best argument

Thomson argued that in the lever case, you are turning an existing threat so that it falls on fewer people. In the footbridge case, you are introducing a new harm to someone who was not in the threat's path at all, and using their body. The distinction between doing and allowing, and between redirecting and initiating, matters morally.

Strongest objection

The distinctions multiply and become hard to state precisely. Thomson herself later changed her mind and argued that the bystander should not pull the lever, since you cannot ask the one person to bear a cost you would not bear yourself.

Defended by

Judith Jarvis Thomson, Frances Kamm

Do nothing

You should not intervene in either case. Killing is worse than letting die, and you have no right to choose who dies.

Best argument

There is a moral difference between killing someone and failing to save them. If you pull the lever, you kill the one; if you do nothing, the trolley kills the five, and you merely fail to prevent it. Many legal systems reflect this difference, and it protects people from being sacrificed whenever someone calculates that it would help others.

Strongest objection

It seems monstrous to let five people die when you could save them at the cost of one, especially when you are not using anyone as a tool. And doing nothing is itself a choice with consequences.

Defended by

Judith Jarvis Thomson (later view)

Where you stand

In the original case, do you pull the lever?

Choose one to see how people answer.

For the full background, variations and open questions, read the entry: The trolley problem.