Bruce J. Krajewski reviews Kant and the Supposed Right to Lie

Jens Timmermann. Kant and the Supposed Right to Lie. Cambridge: Cambridge University Press, 2024. 216 pp.

22 May 2025

Accompanying the Anthropocene is the George Santoscene. We are overrun by lies. Almost every day we see headlines like “This Is How Far Vance Will Go to Sell a Lie”[1] and “Russia Seeds Chatbots with Lies.”[2] It may thus be uplifting to learn that centuries ago the philosopher Immanuel Kant wrote “On a Supposed Right to Lie from Love of Humanity,” an essay in which, in absolutist terms, Kant insists on a duty of truthfulness. In fact, Kant deems lying worse than murder.

He points to the commandment not to lie, which he thought, if enthusiastically adopted by philosophers, could bring about perpetual peace, among other benefits. Oddly, this good news has been drowned out by what Jens Timmermann sees as ill-informed readings of Kant’s 1797 effort. He writes, “Kant’s essay has done more than any of his other works to scare students off his moral theory,” even though it “falls within Kant’s philosophy of law, not his ethics” (pp. xi, 61).

Why the scare? For Timmermann, interpreters strayed from Kant’s message because many became entangled in a thought experiment that has become known as “the murderer at the door,” an instance of the philosophical imaginary almost as famous as the trolley problem. It’s not even Kant’s example. Kant discusses it as part of his response to Benjamin Constant’s 1797 work On Political Reactions. Earlier, in 1750, Johann David Michaelis had also invoked “the murderer at the door.”[3]

The situation involves a potential killer showing up at your house where you have secreted your friend. Somehow, you are aware that someone filled with malevolence is searching for them. An armed murderer comes to the door, though interpreters have failed to note the lack of a door in the example, asking whether you know where your friend is. What do you say? Eminent Kant scholar Christine Korsgaard claims that it is “grotesque” for Kant to insist that the person answering the door be truthful with the murderer (p. xi).

The crux of the matter is “whether a deliberately untruthful assertion can be justified as a means to an end in an emergency” (p. 64). The tension inherent in the thought experiment took on gravitas after World War II when people substituted the murderer at the door with a Nazi officer looking for Jews hidden in people's homes. The question then became: Does Kant really mean to say that people hiding Jews in their homes should have told the truth to the Nazis? Now, for US citizens, the question might be: “Should I tell Immigration and Customs Enforcement officers where my immigrant friend is?”

Timmermann acts as defense attorney, admitting that Kant could have done better with Constant. Chapter 10 is entitled “What Kant Should Have Said.” Timmermann presents evidence from a range of Kant’s works that cumulatively make a reasonable case that Kant generally had it right. Commentators often turn the “murderer at the door” example into a damning dualism, as if the person answering the murderer could only either save the friend by lying or doom the friend to death by telling the truth. Timmermann excels at modeling a wide range of alternative responses, including playing out possible consequences for those alternatives, so that it becomes possible to acknowledge that “Kant’s removal of lying from the householder’s arsenal of defensive resources is much less significant than his readers tend to think” (p. 182).

Timmermann’s book corrects a rush to judgment about Kant’s position on lying. It’s a valuable guide for a wholesale rethinking of the “Supposed Right to Lie.”

[1] Jamelle Bouie, “This Is How Far Vance Will Go to Sell a Lie,” New York Times, 19 Apr. 2025.

[2] Joseph Menn, “Russia Seeds Chatbots with Lies: Any Bad Actor Could Game AI the Same Way,” Washington Post, 17 Apr. 2025.

[3] Timmermann is gobsmacked that “so many of those who write on the Kantian duty of truthfulness appear not to have read Constant’s essay, Michaelis’s inaugural pamphlet, let alone the works of the other major eighteenth-century figures such as Achenwall, Wolff, and Baumgarten” (pp. xiii-xiv).