Violence was first experienced in the church as martyrdom. Under the Roman Empire, Christians were subjected to state-sponsored penalties ranging from fines to corporal punishment to execution. A number of prominent early theologians and apologists fell victim, including Polycarp, Justin Martyr, Origen, Cyprian, Perpetua, and Felicity. With the end of persecution under Constantine and then its eventual designation as the empire’s official religion, Christianity’s relationship to violence changed significantly. While some theologians had attempted to grapple with the question of whether Christians could join the Roman armies, the new relationship between church and state required new theological consideration. Accordingly, new questions arose: For example, could or should the state enforce right belief? Over time, three general approaches to violence emerged.
The first is a coercive model. In this model, the state (and then later, the church in places) used its punitive powers to enforce Christian orthodoxy and fight against its enemies, both within its own borders and externally. St. Augustine provided part of the justification for coercion in his “Letter 93: To Valentius,” in which he argued that not all persecution is evil. If persecution is aimed at bringing one to right belief and practice, it has a positive goal. Many heresy trials and later executions were supported by “Letter 93.” Later thinkers expanded the model of internal persecution against heretics to external attacks on those deemed threatening to Christianity from outside the church or outside the empire. The Crusades were largely justified on such bases.
The second is a pacifist model. Though perhaps the dominant model in the first two centuries of the church, it was quickly eclipsed by the other two perspectives. Early theologians such as Tertullian and Cyprian argued that because Christ forbade Peter to use the sword in the Garden of Gethsemane, Christians were forbidden from using violence to achieve any ends, “but how will a Christian man war, nay, how will he serve even in peace, without a sword, which the Lord has taken away” (Tertullian, On Idolatry, Chapter 19, “On Military Service.”) In the medieval period, the pacifist model was adopted by some monastic traditions (e.g., the Spiritualist Franciscans), but more commonly by what were then considered heretical movements, including the Cathars, Albigensians, Waldensians, and Czech Brethren.
The final model is often called the “Just War” perspective. The origin for this theory can be found in St. Ambrose’s response to a massacre of innocent people. He argued that while a Christian should never use violence for his or her own benefit, there were times when a Christian, out of love for neighbor, had to use violence to protect the weak or innocent. To stand by and watch the powerful attack or kill the innocent when one can do something to prevent it is nearly as great a sin as being one of the attackers. As with the coercive model, Augustine provided much of the framework for this view of violence. Augustine allowed that there were some righteous wars, fought at the command of God as punishment for iniquity. That view remained less influential and is more closely connected to the coercive model. Far more influential was his view that there were wars that were necessary for the protection of the homeland and the innocent. In this sense, he outlined two major principles that guided later thinking. First, a war must have a right (or just) cause (ius ad bellum), and one must fight the war itself justly (ius in bello). Just causes included defending the homeland, coming to the aid of an ally, punishing wicked rulers, or retaking that which was unlawfully stolen. Beyond the simple cause, it also had to be rightly intentioned—it could not be fought for vainglory’s sake, nor to take new lands. It had to have some method of state control, since states go to war, not individual people. When conducting the war, one also had responsibilities. One had to be proportional, have achievable ends, and fight discriminately (that is, between combatants, not combatants against civilian populations). Finally, and most importantly, war had to be a last resort after all other measures failed, and it had to be aimed at producing a benefit for those one sought to defend. In the medieval era, Thomas Aquinas added significant precision to Augustine’s framework.
All three models continued into the Reformation era. The advent of formally competing visions of Christianity following Luther’s excommunication by the pope and his ban by the emperor in 1521 at the Diet of Worms added new dimensions to these models. Martin Luther had occasion to comment upon all three.
Detecting & exploiting positive goal interaction in intelligent agents
