13 In fine, that these precepts pertain rather to the inward disposition of the heart than to the actions which are done in the sight of men, requiring us, in the inmost heart, to cherish patience along with benevolence, but in the outward action to do that which seems most likely to benefit those whose good we ought to seek, is manifest from the fact that our Lord Jesus Himself, our perfect example of patience, when He was smitten on the face, answered: “If I have spoken evil, bear witness of the evil, but if not, why do you smite me?” If we look only to the words, He did not in this obey His own precept, for He did not present the other side of his face to him who had smitten Him but, on the contrary, prevented him who had done the wrong from adding thereto; and yet He had come prepared not only to be smitten on the face, but even to be slain upon the cross for those at whose hands He suffered crucifixion, and for whom, when hanging on the cross, He prayed, “Father, forgive them, they know not what they do!” In like manner, the Apostle Paul seems to have failed to obey the precept of his Lord and Master, when he, being smitten on the face as He had been, said to the chief priest: “God shall smite you, you whited wall, for do you sit to judge me after the law, and commandest me to be smitten contrary to the law?” And when it was said by them that stood near, “Do you revile God's high priest?” he took pains sarcastically to indicate what his words meant, that those of them who were discerning might understand that now the whited wall, i.e. the hypocrisy of the Jewish priesthood, was appointed to be thrown down by the coming of Christ; for He said: “I knew not, brethren, that he was the high priest, for it is written, You shall not speak evil of the ruler of your people;” although it is perfectly certain that he who had grown up in that nation and had been in that place trained in the law, could not but know that his judge was the chief priest, and could not, by professing ignorance on this point, impose upon those to whom he was so well known.
14. These precepts concerning patience ought to be always retained in the habitual discipline of the heart, and the benevolence which prevents the recompensing of evil for evil must be always fully cherished in the disposition. At the same time, many things must be done in correcting with a certain benevolent severity, even against their own wishes, men whose welfare rather than their wishes it is our duty to consult and the Christian Scriptures have most unambiguously commended this virtue in a magistrate. For in the correction of a son, even with some sternness, there is assuredly no diminution of a father's love; yet, in the correction, that is done which is received with reluctance and pain by one whom it seems necessary to heal by pain. And on this principle, if the commonwealth observe the precepts of the Christian religion, even its wars themselves will not be carried on without the benevolent design that, after the resisting nations have been conquered, provision may be more easily made for enjoying in peace the mutual bond of piety and justice. For the person from whom is taken away the freedom which he abuses in doing wrong is vanquished with benefit to himself; since nothing is more truly a misfortune than that good fortune of offenders, by which pernicious impunity is maintained, and the evil disposition, like an enemy within the man, is strengthened. But the perverse and froward hearts of men think human affairs are prosperous when men are concerned about magnificent mansions, and indifferent to the ruin of souls; when mighty theatres are built up, and the foundations of virtue are undermined; when the madness of extravagance is highly esteemed, and works of mercy are scorned; when, out of the wealth and affluence of rich men, luxurious provision is made for actors, and the poor are grudged the necessaries of life; when that God who, by the public declarations of His doctrine, protests against public vice, is blasphemed by impious communities, which demand gods of such character that even those theatrical representations which bring disgrace to both body and soul are fitly performed in honour of them. If God permit these things to prevail, He is in that permission showing more grievous displeasure: if He leave these crimes unpunished, such impunity is a more terrible judgment. When, on the other hand, He overthrows the props of vice, and reduces to poverty those lusts which were nursed by plenty, He afflicts in mercy. And in mercy, also, if such a thing were possible, even wars might be waged by the good, in order that, by bringing under the yoke the unbridled lusts of men, those vices might be abolished which ought, under a just government, to be either extirpated or suppressed.
15. For if the Christian religion condemned wars of every kind, the command given in the gospel to soldiers asking counsel as to salvation would rather be to cast away their arms, and withdraw themselves wholly from military service; whereas the word spoken to such was, “Do violence to no man, neither accuse any falsely, and be content with your wages,” — the command to be content with their wages manifestly implying no prohibition to continue in the service. Wherefore, let those who say that the doctrine of Christ is incompatible with the State's well-being, give us an army composed of soldiers such as the doctrine of Christ requires them to be; let them give us such subjects, such husbands and wives, such parents and children, such masters and servants, such kings, such judges— in fine, even such taxpayers and tax-gatherers, as the Christian religion has taught that men should be, and then let them dare to say that it is adverse to the State's well-being; yea, rather, let them no longer hesitate to confess that this doctrine, if it were obeyed, would be the salvation of the commonwealth.
Source: Letters (New Advent)