I answer that, Several things are requisite for the good of a human society: and a number of things are done better and quicker by a number of persons than by one, as the Philosopher observes (Polit. i, 1), while certain occupations are so inconsistent with one another, that they cannot be fittingly exercised at the same time; wherefore those who are deputed to important duties are forbidden to occupy themselves with things of small importance. Thus according to human laws, soldiers who are deputed to warlike pursuits are forbidden to engage in commerce [*Cod. xii, 35, De Re Milit.].
Now warlike pursuits are altogether incompatible with the duties of a bishop and a cleric, for two reasons. The first reason is a general one, because, to wit, warlike pursuits are full of unrest, so that they hinder the mind very much from the contemplation of Divine things, the praise of God, and prayers for the people, which belong to the duties of a cleric. Wherefore just as commercial enterprises are forbidden to clerics, because they unsettle the mind too much, so too are warlike pursuits, according to 2 Tim. 2:4 : "No man being a soldier to God, entangleth himself with secular business." The second reason is a special one, because, to wit, all the clerical Orders are directed to the ministry of the altar, on which the Passion of Christ is represented sacramentally, according to 1 Cor. 11:26 : "As often as you shall eat this bread, and drink the chalice, you shall show the death of the Lord, until He come." Wherefore it is unbecoming for them to slay or shed blood, and it is more fitting that they should be ready to shed their own blood for Christ, so as to imitate in deed what they portray in their ministry. For this reason it has been decreed that those who shed blood, even without sin, become irregular. Now no man who has a certain duty to perform, can lawfully do that which renders him unfit for that duty. Wherefore it is altogether unlawful for clerics to fight, because war is directed to the shedding of blood.
Reply to Objection 1: Prelates ought to withstand not only the wolf who brings spiritual death upon the flock, but also the pillager and the oppressor who work bodily harm; not, however, by having recourse themselves to material arms, but by means of spiritual weapons, according to the saying of the Apostle ( 2 Cor. 10:4 ): "The weapons of our warfare are not carnal, but mighty through God." Such are salutary warnings, devout prayers, and, for those who are obstinate, the sentence of excommunication.
Reply to Objection 2: Prelates and clerics may, by the authority of their superiors, take part in wars, not indeed by taking up arms themselves, but by affording spiritual help to those who fight justly, by exhorting and absolving them, and by other like spiritual helps. Thus in the Old Testament ( Joshua 6:4 ) the priests were commanded to sound the sacred trumpets in the battle. It was for this purpose that bishops or clerics were first allowed to go to the front: and it is an abuse of this permission, if any of them take up arms themselves.
Reply to Objection 3: As stated above (Q[23], A[4], ad 2) every power, art or virtue that regards the end, has to dispose that which is directed to the end. Now, among the faithful, carnal wars should be considered as having for their end the Divine spiritual good to which clerics are deputed. Wherefore it is the duty of clerics to dispose and counsel other men to engage in just wars. For they are forbidden to take up arms, not as though it were a sin, but because such an occupation is unbecoming their personality.
Reply to Objection 4: Although it is meritorious to wage a just war, nevertheless it is rendered unlawful for clerics, by reason of their being deputed to works more meritorious still. Thus the marriage act may be meritorious; and yet it becomes reprehensible in those who have vowed virginity, because they are bound to a yet greater good.
Whether it is lawful to lay ambushes in war?
Objection 1: It would seem that it is unlawful to lay ambushes in war. For it is written ( Dt. 16:20 ): "Thou shalt follow justly after that which is just." But ambushes, since they are a kind of deception, seem to pertain to injustice. Therefore it is unlawful to lay ambushes even in a just war.
Objection 2: Further, ambushes and deception seem to be opposed to faithfulness even as lies are. But since we are bound to keep faith with all men, it is wrong to lie to anyone, as Augustine states (Contra Mend. xv). Therefore, as one is bound to keep faith with one's enemy, as Augustine states (Ep. ad Bonif. clxxxix), it seems that it is unlawful to lay ambushes for one's enemies.
Objection 3: Further, it is written ( Mat. 7:12 ): "Whatsoever you would that men should do to you, do you also to them": and we ought to observe this in all our dealings with our neighbor. Now our enemy is our neighbor. Therefore, since no man wishes ambushes or deceptions to be prepared for himself, it seems that no one ought to carry on war by laying ambushes.
On the contrary, Augustine says (QQ. in Hept. qu. x super Jos): "Provided the war be just, it is no concern of justice whether it be carried on openly or by ambushes": and he proves this by the authority of the Lord, Who commanded Joshua to lay ambushes for the city of Hai ( Joshua 8:2 ).
I answer that, The object of laying ambushes is in order to deceive the enemy. Now a man may be deceived by another's word or deed in two ways. First, through being told something false, or through the breaking of a promise, and this is always unlawful. No one ought to deceive the enemy in this way, for there are certain "rights of war and covenants, which ought to be observed even among enemies," as Ambrose states (De Officiis i).
Secondly, a man may be deceived by what we say or do, because we do not declare our purpose or meaning to him. Now we are not always bound to do this, since even in the Sacred Doctrine many things have to be concealed, especially from unbelievers, lest they deride it, according to Mat. 7:6 : "Give not that which is holy, to dogs." Wherefore much more ought the plan of campaign to be hidden from the enemy. For this reason among other things that a soldier has to learn is the art of concealing his purpose lest it come to the enemy's knowledge, as stated in the Book on Strategy [*Stratagematum i, 1] by Frontinus. Such like concealment is what is meant by an ambush which may be lawfully employed in a just war.
Nor can these ambushes be properly called deceptions, nor are they contrary to justice or to a well-ordered will. For a man would have an inordinate will if he were unwilling that others should hide anything from him
This suffices for the Replies to the Objections.
Whether it is lawful to fight on holy days?
Objection 1: It would seem unlawful to fight on holy days. For holy days are instituted that we may give our time to the things of God. Hence they are included in the keeping of the Sabbath prescribed Ex. 20:8 : for "sabbath" is interpreted "rest." But wars are full of unrest. Therefore by no means is it lawful to fight on holy days.
Objection 2: Further, certain persons are reproached ( Is. 58:3 ) because on fast-days they exacted what was owing to them, were guilty of strife, and of smiting with the fist. Much more, therefore, is it unlawful to fight on holy days.
Objection 3: Further, no ill deed should be done to avoid temporal harm. But fighting on a holy day seems in itself to be an ill deed. Therefore no one should fight on a holy day even through the need of avoiding temporal harm.
On the contrary, It is written ( 1 Mac. 2:41 ): The Jews rightly determined . . . saying: "Whosoever shall come up against us to fight on the Sabbath-day, we will fight against him."
I answer that, The observance of holy days is no hindrance to those things which are ordained to man's safety, even that of his body. Hence Our Lord argued with the Jews, saying ( Jn. 7:23 ): "Are you angry at Me because I have healed the whole man on the Sabbath-day?" Hence physicians may lawfully attend to their patients on holy days. Now there is much more reason for safeguarding the common weal (whereby many are saved from being slain, and innumerable evils both temporal and spiritual prevented), than the bodily safety of an individual. Therefore, for the purpose of safeguarding the common weal of the faithful, it is lawful to carry on a war on holy days, provided there be need for doing so: because it would be to tempt God, if notwithstanding such a need, one were to choose to refrain from fighting.
However, as soon as the need ceases, it is no longer lawful to fight on a holy day, for the reasons given: wherefore this suffices for the Replies to the Objections.