Can someone here clarify what Kant meant with the following statement:

if you have by a lie prevented someone just now bent on murder from committing the deed, then you are legally accountable for all the consequences that might arise from it. But if you have kept strictly to the truth, then public justice can hold nothing against you, whatever the unforeseen consequences might be

Now I get that lying is considered wrong in Kant's moral philosophy no matter the circumstances. What I don't understand is why Kant believed you are responsible for the consequences of your lies but not of the truth.

So in the "Murderer at the door" scenario, you could either tell the murderer the truth, in which case his enemy will most likely be found and killed, or lie and risk that your lie would end up causing his enemy to be killed.

Why did Kant believe you are not responsible for the consequences of providing someone the truth, but are responsible when providing information you believe is false?

The way I understand it you are morally responsibly only for the act of lying itself, while the murderer is responsible for anything immoral he ends up doing using the information you provided. The fact that you believed the information was false might have helped the murderer find his enemy, but the decision to kill him was still made only by the murderer, who should therefore be fully responsible for the murder.

  • 4
    Because Kant believed in judging actions on their intrinsic character, not on their consequences, he was very much opposed to the consequentialism in ethics. If one commits a wrong act, like lying, they thereby accept moral and legal responsibility for all of its (foreseeable) consequences. But acting right is right no matter what, the consequences be damned. If your lying leads to a murder you are, in part, responsible, although it does not make you a murderer, but if your truth-telling does, you are not. It is a maximalist position, but Kant was willing to stick to it.
    – Conifold
    Commented Aug 30, 2019 at 8:18
  • "A good will is not good because of what it effects or accomplishes, because of its fitness to attain some proposed end, but only because of its volition, that is, it is good in itself and, regarded for itself, is to be valued incomparably higher than all that could merely be brought about by it in favor of some inclination and indeed, if you will, of the sum of all inclinations", Groundwork for the Metaphysic of Morals, 4:394
    – Conifold
    Commented Aug 30, 2019 at 8:34

2 Answers 2


The basic answer is that you have duties towards rationality both in yourself and others.

Thus, you have a duty not to lie to a person who is in front of you, because in Groundwork terms you must treat humanity as an ends and never merely as a means. Since they are a human being and thereby a creature capable of rationality, you have a duty to provide them only with true information -- since to do otherwise is to abuse their rationality.

Later in the Metaphysics of Morals (not the Groundwork), Kant actually identifies the wrong in lying with an abuse of your own rationality, because you are not behaving in a rational manner. Note of course that Kant's understanding of rational differs greatly here from the definition of "rational" that many people might use.

Many contemporary Kantians don't agree with Kant. Some of them admit they are not following Kant but rather Hegel in their definitions of reason such as Jurgen Habermas. Other like Christine Korsgaard believe Kant is offering this sort of thing and we're all misreading him.

One thing missing from your consideration is that Kant does not obligate you to answer the question. You suggest it is (a) tell the truth and people die or (b) lie and people live. But perhaps it is (a), (b), or (c) refuse to answer and you die. Which for Kant might be the best option here since then you do not compromise your rationality.



Assuming you know the intention of the person at the door, it is your moral duty to act to prevent this to the best of your ability. However, acting immoral to prevent it (such as lying) would be (somewhat) immoral, your intentions would not justify your means.

Speaking truths only but not seizing a viable opportunity to prevent the murder is equally immoral.

When you perceive only choices that involve acts that by themselves would be immoral, picking the least immoral one such as lying is a moral choice. But it would not be your intention of preventing a murder that would make it moral, but the absence of other moral means.

None of this implies any full responsibility of you for people murdered. This example just differentiates between moral behavior and (somewhat) immoral behavior, the extend of responsibility is not relevant here for the purpose of the example.

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