World War One: A Just War or Just a War? - Woodrow Wilson Vs. St. Thomas Aquinas

The writings of St. Thomas Aquinas on "just war" were built mainly off of the works of St. Augustine and presented within the Summa Theologica. He declares three requirements must be present to constitute a just war, "In order for a war to be just, three things are necessary. First, the authority of the sovereign by whose command the war is to be waged... Secondly, a just cause is required, namely that those who are attacked, should be attacked because they deserve it on account of some fault... Thirdly, it is necessary that the belligerents should have a rightful intention, so that they intend the advancement of good, or the avoidance of evil,"

St. Thomas points out that people, Christians especially, should never kill for personal dispensation of justice, but it has been assigned the rightful sovereign's duty to execute the law and dispense justices for the good of all. In doing so, people may engage in killing an enemy under an extension of the permission of the state, such as in war.

So long as the sovereign has actual authority to rule the people (and real authority from God, from who all authority derives in the Judeo-Christian belief) the judgments of the state should be assumed rightful in the order of the world for the benefit of all. There must also be some fault that requires retaliation on the part of the aggressor. Most importantly, the cause of the retaliating faction must pursue restoration of order unselfishly with a genuine desire for peace.