ABSTRACT
Jus ad bellum is about whether or not one has a just cause for going to war: whether the war as an enterprise is morally permissible. The first part of this chapter will introduce the seven formal jus ad bellum conditions that are the generally accepted requirements for a just war, and will outline some of the substantive disagreements concerning them. The second part of the chapter will consider in more detail the ways in which contemporary just war theorists have conceived of the substantive content of two of the most controversial jus ad bellum conditions, just cause and proportionality.
