Fourth, it is proved by reason. It is lawful for the commonwealth to defend its citizens from internal enemies of peace by eliminating them with different kinds of punishment, and therefore it will also be lawful to defend its citizens from external enemies by war and weapons when it cannot be done in any other way. Since, in order to preserve themselves, it is necessary for commonwealths to be able to keep away all their enemies, both internal and external, and since this is the law of nature, it is certainly not credible that the ability to defend themselves was removed through the Gospel.
Last, it is proved by the testimonies of the Fathers. Tertullian in Apologeticus, chapter 42, says: “We sail with you, and fight with you, and farm with you, and trade with you.”
St. Gregory of Nazianzus in his third [second] Oratio de pace [22] says: “Both [the time of war and the time of peace] require some consideration, for even though it is actually possible in some cases to fight war in accordance with God’s law and authority, nevertheless for as long as we can we should incline rather to peace as the more divine and sublime course.”
In his homily De nuptiis, on John 2, St. John Chrysostom says, among other things, “You use the army as a pretext and say that you cannot be pious; was not the centurion a soldier, and yet his being in the army did him no harm?”
Blessed Ambrose, sermon 7, says, “to be in the army is not a crime, but to be in the army for the sake of pillaging is a sin.” And in his De officiis, book 1, chapters 40 and 41, he lists among the virtues military valor, and he proves that our men did not lack it with many examples. Likewise in his Oratio de obitu Theodosii he vigorously praises Theodosius for his ability in war.
In his epistle 5 [138] to Marcellinus blessed Augustine says: “For if Christian discipline disapproved all wars, the soldiers in the Gospel who were asking for advice about salvation would have been told to throw away their weapons and to remove themselves completely from the army, but in fact they were told not to do violence to any man, or accuse any falsely, and to be content with their wages. So He commanded that their pay should suffice and certainly did not prohibit them from serving in the army.” And in epistle 205 or 207 [189] to Boniface he says, “Do not think that anybody who serves in the army cannot please God, etc.” He teaches the same in book 22 of his Contra Faustum, chapters 74ff., and book 6, Quaestiones in Iesum Nave, question 10.
Blessed Gregory, in book 1 of the epistles, chapter 72 [epistle 74] to Gennadius,136 says: “Just as the Lord of victories made your excellence shine brightly against the enemies of war in this life, so it is necessary that the same excellence is shown against the enemies of His Church with all vigor of mind and body, etc.,” and in chapter 73 [epistle 75], “If such prosperity had not followed your excellence in warfare as a reward of your faith, and through the grace of the Christian religion, it would not be such a wonder, but since you have made provisions for future victories (God willing) not with carnal precaution, but rather with prayers, it is something wonderful that your glory stems from God, who grants it from above, not from earthly advice.”
Gregory of Tours in Historia, book 5, chapter 1, says: “If only you, O kings, engaged in the same battles as your forefathers, that the heathen terrified by your union might be crushed by your strength!”
Blessed Bernard in his sermon to the soldiers, chapter 3, says: “Indeed the soldiers of Christ confidently fight the battles of their Lord, and have no fear of sinning when killing the enemies, and no fear of incurring the danger of being killed, seeing that death suffered or inflicted for Christ is not a crime but deserves a great glory.”
But against this they object, first, through the Scriptures, starting with Deuteronomy 32: “To me belongeth vengeance and recompence,”137 and Romans 12: “Dearly beloved, avenge not yourselves, but rather give place unto wrath: for it is written, Vengeance is mine; I will repay, saith the Lord.”138 I reply that the vengeance that public authorities seek is rightly called the vengeance of God, for they are ministers of God serving Him in this matter, and that is why Paul, having said, “Vengeance is mine,” at the end of Romans 12, begins chapter 13 by saying, “But if thou do that which is evil, be afraid; for he beareth not the sword in vain: for he is the minister of God, a revenger to execute wrath upon him that doeth evil.”139
Then they add this passage from Isaiah 2: “And they shall beat their swords into plowshares, and their spears into pruning hooks: nation shall not lift up sword against nation, neither shall they learn war any more,”140 which are things predicted of the Christian era. I reply that in this passage only the perfect peace to come at the time of Christ’s birth is predicted, as blessed Jerome explains, and we know that this was fulfilled at the time of Augustus. Those words “any more” do not mean “for eternity,” but “for a long time.” Moreover, even if that had not been fulfilled, nothing could be concluded from it, for Isaiah does not prohibit war if there are enemies who disturb us, but he predicts a time in which there will be no enemies. Therefore as long as there are enemies, war can be waged, as it can also be said that it is predicted that Christ’s kingdom will be peaceful, seeing that His kingdom is not of this world and does not deal with temporal matters, and in this it is distinguished from the Judaic kingdom, which had to be strengthened and preserved with war and killings.
Finally they object with these words in Matthew 5: “But I say unto you, That ye resist not evil: but whosoever shall smite thee on thy right cheek, turn to him the other also,”141 and Matthew 26: “All they that take the sword shall perish with the sword,”142 which are similar to Romans 12, “Recompense to no man evil for evil. Provide things honest in the sight of all men, etc.”143
I reply that Julian the Apostate once used the same arguments against the Christians, as Gregory of Nazianzus reports in the first oration In Julianum [4], around the middle of the work. But first, that all these precepts or counsels are given to private citizens, for God or the apostle did not command the judge not to punish him who wronged another, but He commanded everybody to suffer patiently their wrongs. War, however, does not pertain to private revenge but to public justice, and just as loving one’s enemy, which everybody must, does not prevent the judge and the executioner from doing their duty, so it does not prevent the soldiers and the emperors from doing theirs.
Moreover, even these are not always precepts to private citizens; sometimes they are precepts, sometimes advice. Precepts are always to prepare the soul, so that a man may be ready to turn the other cheek and to give away his coat to somebody who wants it rather than offend God. But such action is in fact prescribed when it is necessarily demanded by God’s honor. Otherwise it is only advice, and sometimes not even that, for instance when offering the other cheek is of no use because the other person just repeats his sin. Such is the response of Gregory of Nazianzus in this passage, and Augustine’s in epistle 5 [138] to Marcellinus.
Second, they can oppose our argument with three decrees of the Church. The first is in the Council of Nicaea, canon 11, where a most serious punishment is inflicted against those who return to the army after leaving it.144 The second is in epistle 90 [167] of blessed Leo, to Rusticus, and it is found also in the canon “Contrarium, de poenitentia,” distinction 5.145 Leo says, “It is contrary to the ecclesiastical rules to return to a secular army after doing penance,” and later, “He who wants to involve himself in worldly warfare is not free from the Devil’s snares.” The third is Gregory’s canon “Falsas,” same distinction, where it is said that those who adopt an activity that cannot be done without sinning are not entitled to do penance unless they abandon such activity, and Gregory gives the example of a soldier.146
To the first I reply that it deals with those who because they confessed their faith were deprived by Diocletian or Licinius of their sword belt, and afterward they reclaimed it, ready to deny their faith. See Zonaras and Balsamon on that canon, and Rufinus, Historia, book 10, chapter 6, and what we wrote on this in book 2 of De Conciliis, chapter 8.
To the second and third I say that it deals with those who committed many sins occasioned