The just-war theory is both bad and good. This is not a contradiction. For nonresistant Christians, it is bad. Pacifism is a way of life,
Suppose you were to ask a Mennonite, “What does Jesus command his followers to do?” Ironically, one common response would come from the Old Testament, or at least Jesus quoting the Old Testament: Love God with all your heart, soul and mind, and love your neighbor as yourself.
