The Murderer at the Door: What Kant Should Have Said

Abstract

Embarrassed by the apparent rigorism Kant expresses so bluntly in ‘On a Supposed Right to Lie,’ numerous contemporary Kantians have attempted to show that Kant’s ethics can justify lying in specific circumstances, in particular, when lying to a murderer is necessary in order to prevent her from killing another innocent person. My aim is to improve upon these efforts and show that lying to prevent the death of another innocent person could be required in Kantian terms. I argue (1) that our perfect Kantian duty of self‐preservation can require our lying to save our own lives when threatened with unjust aggression, and (2) that Kant’s understanding of moral duty was that duties are symmetrical, such that if one has a duty to perform a given action on one’s own behalf or to protect one’s own rational nature, then one also has a duty to perform similar acts on other’s behalf or to protect their rational nature. Thus, that the individual protected against aggression by means of deception is not oneself should be of no consequence from a Kantian perspective. Lying to the murderer is thus an extension of the Kantian requirement of self‐defense.