A Formalization of Kant’s Second Formulation of the Categorical Imperative Felix Lindner Foundations of Artificial Intelligence, University of Freiburg, Germany lindner@informatik.uni-freiburg.de Martin Mose Bentzen Management Engineering, Technical University of Denmark, Lyngby, Denmark mmbe@dtu.dk Abstract We present a formalization and computational implementation of the second formulation of Kant’s categorical imperative. This ethical principle requires an agent to never treat someone merely as a means but always also as an end. Here we interpret this principle in terms of how persons are causally affected by actions. We introduce Kantian causal agency models in which moral patients, actions, goals, and causal influence are represented, and we show how to formalize several readings of Kant’s categorical imperative that correspond to Kant’s concept of strict and wide duties towards oneself and others. Stricter versions handle cases where an action directly causally affects oneself or others, whereas the wide version maximizes the number of persons being treated as an end. We discuss limitations of our formalization by pointing to one of Kant’s cases that the machinery cannot handle in a satisfying way. 1 Introduction It has been suggested that artificial agents, such as social robots and software bots, must be programmed in an ethical way in order to remain beneficial to human be- ings. One prominent ethical theory was proposed by Immanuel Kant [1]. Here, we propose a formalization and implementation of Kant’s ethics with the purpose We would like to thank the three anonymous reviewers for their valuable comments that helped us to improve the paper. Vol. \jvolume No. \jnumber \jyear Journal of Applied Logics — IFCoLog Journal of Logics and their Applications