The Ethics of War: John of Naples and the Use of Muslim Mercenaries by a Christian King

The article analyses the question by John of Naples (d. ca. 1348) of whether it is licit for a Christian King to hire Muslim mercenaries to defend his country against Christian attackers. John’s answer employs legal, theological, and philosophical sources intended to justifying the view that it is indeed licit to do so. John’s original account modifies the just war tradition to qualify his ambitions better and adapts the elements of the legal principle of necessity, which support his argument. His overall ethical account builds on the primacy of the common good, which allows the use of imperfect means, such as hiring Muslim mercenaries, to achieve the good of Christian community in a just war.