Mandeville, LA – [Editor’s note: this is an edited version of St Thomas Aquinas’ Summa, Part II. 2, Question 40, Article 1: Whether it is always sinful to wage war? – On the 17th Anniversary of the 9-11 attacks, its beyond time that Christian Americans learned what a Just War is and demanded our governments learn and abide by it as well.- M.C.]
Part II.2, Question 40, Article 1: Whether it is always sinful to wage war? Objection 3: Further, nothing, except sin, is contrary to an act of virtue. But war is contrary to peace. Therefore war is always a sin.
I answer that: 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. For it is not the business of a private individual to declare war, because he can seek for redress of his rights from the tribunal of his superior. Moreover it is not the business of a private individual to summon together the people, which has to be done in wartime. And as the care of the common weal is committed to those who are in authority, it is their business to watch over the common weal of the city, kingdom or province subject to them. And just as it is lawful for them to have recourse to the sword in defending that common weal against internal disturbances, when they punish evil-doers, according to the words of the Apostle (Rm. 13:4): “He beareth not the sword in vain: for he is God’s minister, an avenger to execute wrath upon him that doth evil”; so too, it is their business to have recourse to the sword of war in defending the common weal against external enemies. Hence it is said to those who are in authority (Ps. 81:4): “Rescue the poor: and deliver the needy out of the hand of the sinner”; and for this reason Augustine says (Contra Faust. xxii, 75): “The natural order conducive to peace among mortals demands that the power to declare and counsel war should be in the hands of those who hold the supreme authority.”
Reply to Objection 3: Those who wage war justly aim at peace, and so they are not opposed to peace, except to the evil peace, which Our Lord “came not to send upon earth” (Mt. 10:34). Hence Augustine says: “We do not seek peace in order to be at war, but we go to war that we may have peace. Be peaceful, therefore, in warring, so that you may vanquish those whom you war against, and bring them to the prosperity of peace.”