Theories of the ‘just war’ often encompass justifications for the motives undergirding the declaration of war as well as for the proper conduct of war. The term ‘just war’ originates in the writing of Saint Augustine of Hippo, the most influential theologian of the early Church. He declared that a just man will wage ‘just wars’.
Conditions for a Just War
In the City of God, which compared the fallen secular world with the perfected world of God’s own kingdom, Augustine wanted to find a way to argue that Christians could participate in war under certain conditions, even though the teachings of Jesus seldom seem to support this. He accordingly declared that a just man will wage ‘just wars’. In sermons and other writings, Augustine argued that Christians were justified in fighting wars either to preserve and protect a peaceful society or to punish evildoers.
In the 13th century, the systematic theologian, Thomas Aquinas, codified the conditions for a just war in his Summa Theologiæ. First, a just war can only be waged by a proper authority, defined as one governing for the common good and in the interests of ultimate peace; second, it must be waged for a just cause and not mere territorial gain or power; and third, it must be fought with just motives on the part of all combatants.
It is this last stipulation that sets Thomas and his theory of the just war apart from his predecessors and reflects the development of the Christian crusading ethos. For Aquinas, writing about a century and a half after the First Crusade, a just war now has to prove its justice by being ordered by a legitimate authority and for a just cause (not just thirst for territorial gains and power); but it must also be fought (echoing Augustine) by just men with just motives. A holy war has to be fought by holy men.
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Power of the Roman Papacy
But how can you be sure that your whole army is holy? This is where the growing political and spiritual power of the Roman papacy comes into play.
The call for the launching of the First Crusade, the authority that legitimated it, was that of the reformed Roman Church, which had begun to proclaim that the pope, as Christ’s vicar, or representative on earth, was empowered by God to call a holy war and promise remission of sins to all those who participated, thereby returning them to the sinless, holy state of a newborn child.
These extraordinary claims have their roots in the late 11th century papacy of Gregory VII, who helped to conceptualize and actualize a theory of papal monarchy. Known today as the Gregorian Reform movement, it had emerged out of a crisis of confidence in the papacy of the time, which was rightly regarded as weak, nepotistic, and corrupt.
This reforming movement was complex and multipronged. But it essentially involved efforts to shore up papal authority by cracking down on the sale of Church offices (a practice known as simony); banning (for the first time) the marriage of parish priests and bishops—partly to avoid imputations of impropriety but mostly to halt the alienation of Church property; and efforts to control the political power of bishops by making their appointment and investiture a prerogative of the papacy and not of secular rulers—the so-called Investiture Controversy.
Equation of Excommunication with Deposition
This project met with considerable resistance, both within the Church, especially among married priests and bishops; and among secular rulers, because it would entail a drastic change to longstanding customs. Ever since the establishment of Christianity as the state religion of the Roman Empire under Constantine, local rulers had acted as the heads of the Church within their own domains, and would choose trusted allies or relatives for powerful positions and ordain them as bishops or abbots.
But, Pope Gregory was claiming that he alone had that authority; and he upped the ante by insisting that adherence to these reforms was not just a matter of policy but of religious dogma, defined as a ‘truth necessary for salvation’. Those rulers who refused to comply—notably his chief adversary, the German emperor Henry IV—could therefore be declared excommunicate. Moreover, as Gregory claimed, an excommunicated ruler was no longer a confirmed Christian, and therefore his subjects had a right, a sacred duty, to rebel against his regime.
The equation of excommunication with deposition had given the pope a powerful new weapon to use against wayward rulers. According to a series of pronouncements issued in his name, known as the Dictatus papae or ‘Dictates of the Pope’, Gregory further insisted that the pope alone has the power to judge all men, though he cannot himself be judged by any earthly authority. Moreover, he has the power to free any man from obligations to his lord, because every Christian owes ultimate loyalty to the pope, the arbiter of eternal life or death.
Common Questions about Roman Papacy and Theories of ‘Just Wars’
The theologian Thomas Aquinas codified the conditions for a just war in his Summa Theologiæ: First, a just war can only be waged by a proper authority, defined as one governing for the common good and in the interests of ultimate peace; second, it must be waged for a just cause and not mere territorial gain or power; and third, it must be fought with just motives on the part of all combatants.
The Roman Church proclaimed that the pope, as Christ’s vicar, or representative on earth, was empowered by God to call a holy war and promise remission of sins to all those who participated.
The Gregorian Reform movement involved efforts to shore up papal authority by cracking down on the sale of Church offices; banning the marriage of parish priests and bishops; and efforts to control the political power of bishops by making their appointment and investiture a prerogative of the papacy and not of secular rulers.