What makes an action right · Quiz question 12/35

The Murderer at the Door

The Murderer at the Door

Someone who wants to hurt your friend asks where they're hiding. Can you lie? The Kant–Constant debate behind the murderer at the door.

As it appears in the quiz

Your friend is hiding in your house. Someone who wants to hurt them knocks on your door and asks where they are.

Lying is the right thing to do here.

Who came up with it

In 1797 French politician Benjamin Constant criticized a Kant-style view: if the duty to tell the truth were absolute, you couldn't even lie to a murderer chasing your friend. Kant answered the same year in "On a Supposed Right to Lie from Philanthropy," insisting that lying isn't permitted even then.

Original papers & key readings

What it's really asking

For most people, the answer seems obvious: lying to save your friend is right. That's why this case is often cited as a weak spot in Kant's ethics. For consequentialists it's easy — the lie produces the better outcome.

Kant scholars try to read him more carefully. In a 1986 paper, Christine Korsgaard argued one version of the categorical imperative (the universal law formula) can permit lying to someone like the murderer, who is exploiting our honesty. On W. D. Ross's pluralism, the duty of honesty clashes with the duty to prevent harm, and here the second is weightier.

Where philosophers stand

Consequentialism (lie)

Your friend's life is at stake. If the lie leads to a better outcome, it's right.

Key names: Jeremy Bentham, Peter Singer

Pluralist deontology (lie)

Honesty is only a prima facie duty — it gives way to a weightier duty to prevent harm.

Key names: W. D. Ross, Korsgaard (reinterpreting Kant)

Strict Kantianism (no lying)

Truthfulness is an unconditional duty to everyone. Make exceptions for outcomes and the duty itself collapses.

Key names: Kant (1797)

Philosophers to check out

Sources