I've heard two versions of this anecdote about Kant's ethics:

You are at home and a man with an axe rings the bell. He asks where your children are so that he can kill them. It is, according to Kant, not allowed to lie to the man.

There's a war going on and you have a hider in your house. Troops come in and ask if you have, because it's illegal to have a hider and they want hiders to kill them. It is, according to Kant, not allowed to lie to the troops.

Is it true that Kant would say these things? If so, what's his reasoning?

  • Wouldn't it be a false dilemma to choose between lying and telling them what they want? [line break] In the first example, wouldn't a simple: "I don't intend to give you that information" be ethical under Kant? [line break] However, in the second example I could see how refusing to disclose whether you have a hider or not would present a higher risk; wouldn't a simple objection suffice to provide both a limited protection to the hider, while remaining honest? – Fabián Heredia Montiel Apr 19 '13 at 0:59
  • I am not a practising Christian. But can we answer by saying that each man must must carry his own cross? – Alex Mar 28 '18 at 6:48
  • @Alex, he is interested especially in how kantianism faces that problem. There are people who disagree with kantianism, would their answer be relevant here? – rus9384 Mar 28 '18 at 10:14
  • Kant;s imperative allows us to lie if it serves the greater good. It is Kant's interpretation that we should never lie and in my opinion he made a terrible mistake by suggesting this. – PeterJ Mar 28 '18 at 11:18

I think I found the exact answer for you:

One of the first major challenges to Kant's reasoning came from the French philosopher Benjamin Constant, who asserted that since truth telling must be universal, according to Kant's theories, one must (if asked) tell a known murderer the location of his prey. This challenge occurred while Kant was still alive, and his response was the essay On a Supposed Right to Tell Lies from Benevolent Motives (sometimes translated On a Supposed Right to Lie because of Philanthropic Concerns). In this reply, Kant agreed with Constant's inference, that from Kant's premises one must infer a moral duty not to lie to a murderer. Kant denied that such an inference indicates any weakness in his premises: not lying to the murderer is required because moral actions do not derive their worth from the expected consequences. He claimed that because lying to the murderer would treat him as a mere means to another end, the lie denies the rationality of another person, and therefore denies the possibility of there being free rational action at all. This lie results in a contradiction in conceivably and therefore the lie is in conflict with duty. It is possible to conceive of solutions to the problem according to Kantian ethics: one could, for instance, tell the murderer truthfully that they need to protect the person and thus cannot reveal their location. Because such an action might save the potential victim without treating the murderer merely as a means to that end, it seems a more likely candidate as a maxim of action.

  • The last two sentences no longer appear in the Wikipedia entry... I suggest finding a more stable reference, friend. – elliot svensson Mar 28 '18 at 14:22


Naturally, being rational requires not contradicting oneself, but there is no self-contradiction in the maxim “I will make lying promises when it achieves something I want”. An immoral action clearly does not involve a self-contradiction in this sense (as would the maxim of finding a married bachelor). Kant's position is that it is irrational to perform an action if that action's maxim contradicts itself once made into a universal law of nature. The maxim of lying whenever it gets what you want generates a contradiction once you try to combine it with the universalized version that all rational agents must, by a law of nature, lie when it gets what they want.

See, also for "how this might work", the SEP. Alternatively:

Kant asserted that lying, or deception of any kind, would be forbidden under any interpretation and in any circumstance. In Groundwork, Kant gives the example of a person who seeks to borrow money without intending to pay it back. This is a contradiction because if it were a universal action, no person would lend money anymore as he knows that he will never be paid back. The maxim of this action, says Kant, results in a contradiction in conceivability (and thus contradicts perfect duty). With lying, it would logically contradict the reliability of language. If it is universally acceptable to lie, then no one would believe anyone and all truths would be assumed to be lies. The right to deceive could also not be claimed because it would deny the status of the person deceived as an end in itself. The theft would be incompatible with a possible kingdom of ends. Therefore, Kant denied the right to lie or deceive for any reason, regardless of context or anticipated consequences.


PS: Not counting Fichte, Schelling, Hegel, Herder and Schopenhauer,* Kant, I think, didn't have children. I guess that would have made it easy for him to answer such questions in such ways. (And perhaps including Fichte et alii wouldn't make a difference either.)


This exact situation was navigated by none other than Jesus. The last time he entered Jerusalem, the Pharisees were trying to locate Jesus so that they could let kangaroo justice run its course and get him killed. They enlisted the help of the Romans, who governed the city, making finding Jesus a government imperative, which Judas obeyed. Yet there are few who regard Judas' actions in providing the governors this bit of intelligence as the right thing to do.

Soon thereafter, Jesus was being interrogated in court by Pontius Pilate and also Herod, where he exercised his right to remain silent. Unlike with Judas, I can't think of anybody who says he was doing something wrong by remaining silent under this questioning.

The relevant Commandment (of the ten) is "do not bear false witness". I think people who are troubled by these paradoxes overlook the word "bear". By not speaking, Jesus doesn't incur the burden of proof or shirk his obligation to tell the truth.

From this paper written about Kant's position on the matter, we read that according to Kant,

. . . 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. It is still possible that, after you have honestly answered “yes” to the murderer’s question as to whether his enemy is at home, the latter has nevertheless gone out unnoticed, so that he would not meet the murderer and the deed would not be done; but if you had lied and said that he is not at home, and he has actually gone out (though you are not aware of it), so that the murderer encounters him while going away and perpetrates his deed on him, then you can by right be prosecuted as the author of his death. For if you had told the truth to the best of your knowledge, then neighbors might have come and apprehended the murderer while he was searching the house for his enemy and the deed would have been prevented. Thus one who tells a lie, however well disposed he may be, must be responsible for its consequences even before a civil court and must pay the penalty for them, however unforeseen they may have been; for truthfulness is a duty that must be regarded as the basis of all duties to be grounded on contract, the laws of which is made uncertain and useless if even the least exception to it is admitted.

To be truthful (honest) in all declarations is therefore a sacred command of reason prescribing unconditionally, one not to be restricted by any conveniences. (page 3 of the pdf)

So according to Kant, Judas avoided the guilt of lying. But I'm not convinced that Kant would acquit Judas... after all, he was not obligated to get up from dinner, walk across town, and make an arrangement with the Pharisees as to how they could find Jesus. In contrast, Jesus didn't "tell the truth" under questioning, but he was truthful in all declarations, as required by Kant.

There should therefore be no trouble applying Kant's ethics to the subject paradoxes... just don't answer the question. Die first, but don't answer the question.

Reference: Journal of Social Philosophy, Vol. 41 No. 4, Winter 2010, 403–421. "Kant and the Murderer at the Door... One More Time: Kant’s Legal Philosophy and Lies to Murderers and Nazis" by Helga Varden PDF LINK

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    Just to be clear, I'd suggest consulting a lawyer on public justice and the civil courts, rather than this. In the legal systems I'm aware of, lying is not per se illegal or actionable, and it's possible that telling the strict truth might involve being an accomplice to a criminal act. – David Thornley Dec 20 '18 at 19:20

wikipedia has

The rational capacity that underlies deciding what is moral is called pure practical reason, to be contrasted with pure reason (the capacity to know without having been shown) and mere practical reason (which allows us to interact with the world in experience). Hypothetical imperatives tell us which means best achieve our ends. They do not, however, tell us which ends we should choose.

Kant was interested in formulating a rigorous basis for pure practical reason. His Categorical Imperative in his first formulation is a solution to this problem. It goes like this:

Act only according to that maxim whereby you can, at the same time, will that it should become a universal law.

To genuinely see how Kants ethics apply to the particular situation that you mention, one has to universalise the example. That is it should not be tied down to the particular identity of the person. It should apply to all. When this is done and it does not result in a logical contradiction or a negation then one can rationally and justifiably follow the maxim for this situation. So instead of just one man confronted with an axeman intent on murdering his children, one should consider all men confronted with such an axeman. If the men do not lie, all the children of men will be murdered. This is a negation as then mankind dies out. So one should not follow this maxim here.

Lying in a particular situation should not be confused with lying generally. When lying generally is universalised the, same reasoning as above shows that it negates itself as no meaning can be carried by language. This is at the root of the confusion that your examples are hinting at.

In his second formulation he states that such a rational action must set before it not only a principle but also an end - that is an aim. The action must have intentionality. From this Kant deduces a general maxim: A person must always be an end and never a means (otherwise this would contradict the principle above). Again, this disallows lying. To allow the axeman his intent denies the humanity of his children, he is not treating them as ends in themselves but merely as means to satisfy the axeman whimsical murderous intent.

Finally, in his third formulation, Kant introduces his Kingdom of Ends in which all people should consider themselves both means and ends.

Act in such a way that you treat humanity, whether in your own person or in that of another, always at the same time as an end and never merely as a means.

He states that we ought to act only by maxims that would harmonize with a possible kingdom of ends. By the above, this again disallows lying in the first situation you mention.

(For the SF cognescenti: In passing it occurs to me this is where Asimov probably sourced his infamous laws of Robotics).

To my mind this is simply a rational exegesis and founding of the Christian maxim - love thy neighbour; and the Kingdom of Ends is Christianitys Kingdom of God.

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