  The most famous theory of deontological ethics is Kant’s. Kant’s categorical imperative is formulated as follows: “Act according to that maxim by which you can at the same time will that it should become a universal law” (Kant 1990, 38). It is difficult to supply content to this imperative. Thus, it is not clear that the Kantian imperative can be used to rule out war. Indeed, Kant is a defender of a version of the just war theory, in part because he believes that states have a duty to defend their citizens. Although Kant is not himself a pacifist, one might be able to ground pacifism in Kant’s alternative version of the moral law: “Act so that you treat humanity, whether in your own person or in that of another, always as an end and never as a means only” (Kant 1990, 46). Some pacifists use the second formulation of the categorical imperative to support their position by claiming that war treats persons as means and does not respect them as ends in themselves. One version of this idea has been defended by Soran Reader, who argues that the basic presumption of the “moral status of persons” leads to pacifism. Although Reader argues that one can arrive at this perspective from both a consequentialist approach and a Kantian one, she relies on the basic intuition that respect for persons as ends in themselves requires us not to kill them. It is possible to use this deontological principle to support a maximal extension of pacifism such that the prohibition against killing might be extended to include a prohibition against killing non-human persons. This interpretation would obviously require a further analysis of the notion of personhood. Another version of deontological pacifism has been defended by Robert Holmes who claims that morality, properly speaking, focuses on individuals, while war focuses on defending collectives, which are not the proper focal point of morality (Holmes 2017b). 