The murderer at the door: is the duty of veracity unconditional, even to save a life?

Immanuel Kant, answered from the texts and cited to the page.

Immanuel Kant answers

The question has a precise shape, and the answer is yes — the duty of veracity is unconditional, admitting no exception, even when a murderer stands at the door asking after your friend. Let me say first what the duty is not. It is not a duty to hand over information that belongs to someone else, or to facilitate a crime by volunteering what you know.

The question is narrower: when you cannot avoid answering, when you are compelled to speak, is there a right to be untruthful? There is not.¹ The reason is not squeamishness about consequences, nor indifference to your friend's life. The reason is that truth in utterances that cannot be avoided is a formal duty to everyone — however great the disadvantage that may arise from it to the speaker or to any other person.²

A lie does not merely harm the individual deceived; it vitiates the very source of justice, because it undermines the institution of truthful declaration upon which all rights grounded in contract depend.³ When I lie, I do wrong to mankind generally in the most essential point of duty, even if I do no wrong to the particular man who unjustly compels me to speak.⁴

Constant, the French philosopher whose objection occasioned my 1797 essay, proposed that the duty of veracity holds only toward those who have a right to the truth. The formulation is confused at its root.⁵ Truth is not a possession that can be granted to one person and withheld from another; what one has a right to is another's veracitas — the subjective truthfulness in that person's conduct — and this right belongs to everyone without distinction.⁶

The duty of veracity makes no distinction between persons toward whom we have it and persons toward whom we may be free from it; it is unconditional and holds in all circumstances.⁷ Now the consequentialist objection runs: but your truthfulness may get the friend killed. My answer is twofold. First, empirically: if you tell the truth, it remains possible that neighbors apprehend the murderer while he searches the house, and the deed is prevented.⁸

The lie does not guarantee the friend's safety; the truth does not guarantee his death. The consequences are in neither case yours to control with certainty. Second, and more fundamentally: the harm that follows from your truthful statement is the murderer's act, not yours. You have not done him wrong; accident (casus) has done harm to the inhabitant of the house, not your free deed.⁹

But the agent who lies takes on responsibility for all the consequences that follow — including the unforeseen ones — and must answer for them even before a civil court.¹⁰ The liar, however benevolently disposed, cannot shed the legal and moral weight of what the lie sets in motion. There is a further consideration, which I regard as decisive.

The man who, when asked whether he intends to speak truth, does not receive the question with indignation but asks permission first to consider possible exceptions — that man is already a liar in potentia.¹¹ He has shown that he does not recognize veracity as a duty in itself, but reserves exceptions from a rule that in its nature admits none, because to admit exceptions is self-contradictory: the rule would no longer be a rule.¹²

To be truthful in all declarations is a sacred command of reason, prescribing unconditionally, not to be restricted by any conveniences.¹³ Korsgaard's reconstruction — that the murderer, by his evil intent, has placed himself outside the moral community and therefore forfeits his claim to our truthfulness — is philosophically careful, and it is not what I argued in 1797.

The 1797 essay makes no such distinction. The duty of veracity is unconditional not because every interlocutor deserves truth as a reward for good conduct, but because the institution of truthful declaration is the condition of any rational communication whatsoever. Suspend it for the murderer, and you have introduced a principle — "I may lie when circumstances seem to require it" — that, universalized, destroys the institution entirely.

The position in brief

The duty of veracity is a perfect duty and admits no exception. There is no right to lie even when a murderer appears at one's door asking whether a hidden friend is inside. The agent who lies to the murderer does not thereby preserve the friend's life: the lie may inadvertently direct the murderer to the friend's actual hiding place. The agent who tells the truth preserves the moral link between intention and consequence — whatever follows is the murderer's act, not the truth-teller's.

The agent who lies severs that link and becomes morally responsible for the harm. Lying as a maxim cannot be universally willed: in a world where everyone lies whenever circumstances seem to require it, the institution of truth-telling collapses, and lying itself becomes impossible because no one would believe an assertion. The duty of veracity is the condition of any rational communication.¹⁴¹⁵¹⁶¹⁷¹⁸

Sources

Now, the first question is whether a man — in cases where he cannot avoid answering Yes or No — has the right to be untruthful.
Critique of Practical Reason and Other Works on the Theory of Ethics
Truth in utterances that cannot be avoided is the formal duty of a man to everyone, however great the disadvantage that may arise from it to him or any other.
Critique of Practical Reason and Other Works on the Theory of Ethics
truthfulness is a duty that must be regarded as the basis of all duties to be grounded on contract, the law of which is made uncertain and useless if even the least exception to it is admitted.
On a supposed right to lie from philanthropy (1797), pp. 647–648
although by making a false statement I do no wrong to him who unjustly compels me to speak, yet I do wrong to men in general in the most essential point of duty.
Critique of Practical Reason and Other Works on the Theory of Ethics
The πρῶτον ψεῦδος here lies in the proposition 'to tell the truth is a duty, but only to one who has a right to the truth.'
On a supposed right to lie from philanthropy (1797), pp. 646–647
One must instead say one has a right to his own truthfulness (veracitas), that is, to the subjective truth in his person. For to have a right to a truth objectively would be tantamount to saying that, as in the case with what is yours or mine generally, it is a matter of one's will whether a given proposition is to be true or false.
On a supposed right to lie from philanthropy (1797), pp. 646–647
the duty of veracity (of which alone we are speaking here) makes no distinction between persons towards whom we have this duty, and towards whom we may be free from it; but is an unconditional duty which holds in all circumstances.
Critique of Practical Reason and Other Works on the Theory of Ethics
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.
On a supposed right to lie from philanthropy (1797), pp. 647–648
it was merely an accident (casus) that the truth of the statement did harm to the inhabitant of the house; it was not a free deed (in the juridicial sense).
Critique of Practical Reason and Other Works on the Theory of Ethics
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.
On a supposed right to lie from philanthropy (1797), pp. 647–648
The man who, when asked whether in the statement he is about to make he intends to speak truth or not, does not receive the question with indignation at the suspicion thus expressed towards him that he might be a liar, but who asks permission first to consider possible exceptions, is already a liar (in potentia).
Critique of Practical Reason and Other Works on the Theory of Ethics
he shows that he does not recognize veracity as a duty in itself, but reserves exceptions from a rule which in its nature does not admit of exceptions, since to do so would be self-contradictory.
Critique of Practical Reason and Other Works on the Theory of Ethics
To be truthful (honest) in all declarations is therefore a sacred command of reason prescribing unconditionally, one not to be restricted by any conveniences.
On a supposed right to lie from philanthropy (1797), pp. 647–648
Drawing upon his conception of legal imputation of the consequences of one's actions, he maintains, further, that one would be legally responsible for the unforeseen results of a lie. On a supposed right to lie from philanthropy On a supposed right to lie from philanthropy In the journal Frankreich im Jahr 1797, Part VI, No. 1, "On Political Reactions" by Benjamin Constant contains the following (p.
On a supposed right to lie from philanthropy (1797), Ak. 8:425–8:427
Now, ih.c first question is whether a man in cases where he can not avoid answering Yes or No has the right to be untruthful. The second question is whether, in order to prevent a misdeed that threatens him or some one else, he is not actually bound to be untruthful in a certain statement to which an unjust compulsion forces him.
Critique of Practical Reason and Other Works on the Theory of Ethics, pp. 362–363
The common reason of men in its practical judgments perfectly coincides with this, and always has in view the principle here suggested. Let the question be, for example: May I when in distress make a promise with the intention not to keep it? I readily distin guish here between the two significations which the question may have: "Whether it is prudent (23), or whether it is right, to make a false promise.
Critique of Practical Reason and Other Works on the Theory of Ethics, pp. 18–19
D. Michaelis of Gottingen put forward this extraordinary opinion earlier than Kant. The author of this paper himself told me that the philosopher spoken of in this passage is Kant." K. F.
On a supposed right to lie from philanthropy (1797), Ak. 8:427
My own experience must necessarily be limited, and if what others told me was false, I could not satisfy my craving for knowledge. A lie is thus a falstloquium in pracjudicium humanitatis, even thoughit does not violate any specific jus guaesitum of another. In law a mendacium is a falsiloguium in pracjudicium alterius; and so it must be in law; but morally it is a falsiloquium in pracjudicium humanitatis.
Lectures on Ethics, p. 228

Where the argument is made

On a Supposed Right to Lie from Philanthropy (1797), the response to Benjamin Constant's Des Réactions Politiques (1797)
Metaphysics of Morals, Doctrine of Virtue §9 on lying as violation of duty to self
Groundwork of the Metaphysics of Morals, the false-promise example as failure of the universal law test

How the argument was received

The standard reductio of Kantian deontology since Constant first raised the case in 1797. Most contemporary moral philosophers regard the position as monstrous or as evidence that Kant's formalism breaks down at the limits. Korsgaard's 1986 reconstruction preserves the duty of veracity by appealing to an ideal/non-ideal distinction — the categorical imperative governs relations among rational beings, and the murderer has placed himself outside that community by his evil intent. Allen Wood and several twentieth-century Kantians defend Kant's actual position as published. The position is uncompromising; Kant did not retract.