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CHAPTER II: Of the causes of war. - Jean-Jacques Burlamaqui, The Principles of Natural and Politic Law 
The Principles of Natural and Politic Law, trans. Thomas Nugent, ed. and with an Introduction by Peter Korkman (Indianpolis: Liberty Fund, 2006).
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Of the causes of war.
I. If war be sometimes lawful, and even necessary, as we have already demonstrated; this is to be understood when it is undertaken only for just reasons, and on condition that the prince, who undertakes it, proposes, by that method, to obtain a solid and lasting peace. A war may therefore be either just or unjust, according to the cause which has produced it.
II. A war is just if undertaken for just reasons; and unjust if it be entered into without a cause, or at least without a just and sufficient motive.
III. To illustrate the matter, we may, with Grotius, distinguish between the justifying reasons, and the motives of the war. The former are those which render, or seem to render, the war just with respect to the enemy, so that in taking up arms against him we do not think we do him injustice.<230> The latter are the views of interest which determine a prince to come to an open rupture. Thus in the war of Alexander against Darius, the justifying reason of the former was, to revenge the injuries which the Greeks had received from the Persians. The motives were, the ambition, vanity, and avarice of that conqueror, who took up arms the more chearfully, as the expeditions of Xenophon and Agesilaus made him conceive great hopes of success. The justifying reason of the second Punic war was, a dispute about the city of Saguntum. The motive was, an old grudge entertained by the Carthaginians against the Romans for the hard terms they were obliged to submit to when reduced to a low condition, and the encouragement given them by the success of their arms in Spain.1
IV. In a war, perfectly just, the justifying reasons must not only be lawful, but also be blended with the motive; that is, we must never undertake a war but from the necessity of defending ourselves against an insult, of recovering our undoubted right, or of obtaining satisfaction for a manifest injury.
V. Thus a war may be vicious or unjust, with respect to the causes, four different ways.
1°. When we undertake it without any just reason, or so much as an apparent motive of advantage, but only from a fierce and brutal fury, which delights in blood and slaughter. But it may be doubted, whether we can find an example of so barbarous a war.2 <231>
VI. 2°. When we attack others only for our own interest, without their having done us any injury; that is, when we have no justifying causes: and these wars are, with respect to the aggressor, downright robberies.
VII. 3°. When we have some motives founded on justifying causes, but which have still only an apparent equity, and when well examined, are found at the bottom to be unlawful.
VIII. 4°. Lastly, we may say that a war is also unjust, when, though we have good justifying reasons, yet we undertake it from other motives, which have no relation to the injury received; as for instance, through vain glory, or the desire of extending our dominions, &c.
IX. Of these four sorts of war, the undertaking of which includes injustice, the third and last are very common, for there are few nations so barbarous as to take up arms without alledging some sort of justifying reasons. It is not difficult to discover the injustice of the third; as to the fourth, though perhaps very common, it is not so much unjust in itself, as with respect to the view and design of the person who undertakes it. But it is very difficult to convince him of it, the motives being generally impenetrable, or at least most princes taking great care to conceal them.* <232>
X. From the principles here established we may conclude, that every just war must be made, either to defend ourselves and our property against those who endeavour to injure us by assaulting our persons, and by taking away or ruining our estates; or to constrain others to yield up to us what they ought to do, when we have a perfect right to require it of them; or lastly, to obtain satisfaction for the damages we have injuriously sustained, and to force those who did the injury to give security for their good behaviour.
XI. From hence we easily conceive what the causes of war may be. But to illustrate the subject still further, we shall give some examples of the principal unjust causes of war.
1°. Thus, for example, to have a just reason for war, it is not sufficient that we are afraid of the growing power of a neighbour. All we can do, in those circumstances, is innocently to try to obtain real caution, that he will attempt nothing against us; and to put ourselves in a posture of defence. But acts of hostility are not permitted, except when necessary, and they are never necessary so long as we are not morally certain that the neighbour we dread has not only the power, but also the inclination to attack us. We cannot, for instance, justly declare war against a neighbour, purely because he orders citadels or fortifications to be erected, which he may some time or other employ to our prejudice.3
XII. 2°. Neither does utility alone give the same right as necessity, nor is it sufficient to render<233> a war lawful. Thus, for example, we are not allowed to take up arms with a view to make ourselves masters of a place which lies conveniently for us, and is proper to cover our frontiers.4
XIII. 3°. We must say the same of the desire of changing our former settlements, and of removing from marshes and deserts to a more fertile soil.
4°. Nor is it less unjust to invade the rights and liberty of a people, under a pretext of their not being so polished in their manners, or of such quick understanding as ourselves. It was therefore unjust in the Greeks to treat those, whom they called Barbarians, as their natural enemies, on account of the diversity of their manners, and perhaps because they did not appear to be so ingenious as themselves.5
XIV. 5°. It would also be an unjust war to take up arms against a nation, in order to bring them under subjection, under pretence of its being their interest to be governed by us. Though a thing may be advantageous to a person, yet this does not give us a right to compel him to it. Whoever has the use of reason, ought to have the liberty of choosing what he thinks advantageous to himself.6
XV. We must also observe, that the duties which nations ought to practise towards each other, are not all equally obligatory, and that their deficiency in this respect does not always lay a foundation for a just war. Among nations, as well as individuals, there are duties attended with a rigorous and perfect obligation, the violation of which implies an injury<234> properly so called; and duties of an imperfect obligation, which give to another only an imperfect right. And as we cannot, in a dispute between individuals, have recourse to courts of law to recover what in this second manner is our due; so neither can we, in contests between different powers, constrain them by force of arms.
XVI. We must however except from this rule, the cases of necessity in which the imperfect is changed into the perfect right; so that, in those cases, the refusal of him, who will not give us our due, furnishes us with a just reason for war. But every war, undertaken on account of the refusal of what a man is not obliged by the laws of humanity to grant, is unjust.7
XVII. To apply these principles, we shall give some examples. The right of passing over the lands of another is really founded on humanity, when we design to use that permission only on a lawful account; as when people, expelled their own country, want to settle elsewhere; or when, in the prosecution of a just war, it is necessary to pass through the territories of a neutral nation, &c. But this is only an office of humanity which is not due to another in virtue of a perfect and rigorous right, and the refusal of it does not authorise a nation to challenge it in a forcible manner.8
XVIII. Grotius however, examining this question, pretends, “that we are not only obliged to grant a passage over our lands to a small number of men<235> unarmed, and from whom we have consequently nothing to fear; but moreover that we cannot refuse it to a large army, notwithstanding the just apprehension we may have that this passage will do us a considerable injury, which is likely to arise either from that army itself, or from those against whom it marches: provided,” continues he, “1°. that this passage is asked on a just account. 2°. That it is asked before an attempt is made to pass by force.”
XIX. This author then pretends, that, under those circumstances, the refusal authorises us to have recourse to arms, and that we may lawfully procure by force, what we could not obtain by favour, even though the passage may be had elsewhere by taking a larger circuit. He adds, “That the suspicion of danger from the passing of a great number of armed men, is not a sufficient reason to refuse it, because good precautions may be taken against it. Neither is the fear of provoking that prince, against whom the other marches his army, a sufficient reason for refusing him passage, if the latter has a just reason for undertaking the war.”
XX. Grotius founds his opinion on this reason, that the establishment of property was originally made with the tacit reservation of the right of using the property of another in time of need, so far as it can be done without injuring the owner.
XXI. But I cannot embrace the opinion of this celebrated writer; for, 1°. whatever may be said, it<236> is certain that the right of passing through the territories of another is not a perfect right, the execution of which can be rigorously demanded. If a private person is not obliged to suffer another to pass through his ground, much less is a nation obliged to grant a passage to a foreign army, without any compact or concession intervening.
XXII. 2°. The great inconveniencies which may follow such a permission, authorise this refusal. By granting such a passage, we run a risque of making our own country the seat of war. Besides, if they, to whom we grant the passage, are repulsed and vanquished, let the reasons they had for making war be ever so just, yet will not the enemy revenge himself upon us who did not hinder those troops from invading him? But farther, suppose that we live in friendship with both the princes who are at war, we cannot favour one to the prejudice of the other, without giving this other a sufficient reason to look upon us as enemies, and as defective in that part of our duty which we owe to our neighbours. It would be in vain, on this occasion, to distinguish between a just and an unjust war, pretending that the latter gives a right of refusing the passage, but that the former obliges us to grant it. This distinction does not remove the difficulty; for, besides that it is not always easy to decide whether a war be just or unjust, it is a piece of rashness to thrust in our arbitration between two armed parties, and to intermeddle with their differences.9
XXIII. 3°. But is there nothing to fear from the<237> troops to whom the passage is granted? The abettors of the contrary opinion agree there is, for which reason they allow that many precautions ought to be observed. But whatever precautions we may take, none of them can secure us against all events; and some evils and losses are irreparable. Men that are always in arms are easily tempted to abuse them, and to commit outrages; especially if they be numerous, and find an opportunity of making a considerable booty. How often have we seen foreign armies ravage and appropriate to themselves the estates of a people who have called them to their assistance? Nor have the most solemn treaties and oaths been able to deter them from this black perfidiousness.* What then may we expect from those who are under no such strict engagement?
XXIV. 4°. Another observation we may make, which is of great use in politics, that almost all states have this in common, that the further we advance into the heart of a country, the weaker we find it. The Carthaginians, otherwise invincible, were vanquished near Carthage by Agathocles and Scipio. Hannibal affirmed, that the Romans could not be conquered except in Italy. It is therefore dangerous to lay open this secret to a multitude of foreigners, who, having arms at hand, may take advantage of our weakness, and make us repent our imprudence.
XXV. 5°. To this we must add, that in every state there are almost always mutinous and turbulent spirits, who are ready to stir up strangers either against their<238> fellow-citizens, their sovereign, or their neighbours. These reasons sufficiently prove, that all the precautions which can be taken cannot secure us from danger.
6°. Lastly, we may add the example of a great many nations, who have been very ill requited for letting foreign troops pass through their country.
XXVI. We shall finish the examination of this question by making two remarks. The first is, that it is evident from the whole of what has been said, that this is a matter of prudence; and that though we are not obliged to grant a passage to foreign troops, and the safest way is to refuse it, yet when we are not strong enough to resist those who want to pass at any rate, and by resisting we must involve ourselves in a troublesome war, we ought certainly to grant a passage; and the necessity to which we are reduced, is a sufficient justification to the prince whose territories those troops are going to invade.10
XXVII. My second remark is, that if we suppose, on one hand, that the war which the prince, who demands a passage through our country, makes, is just and necessary, and, on the other, that we have nothing to fear either from him that is to pass, or him against whom he marches; we are then indispensably obliged to grant a passage. For if the law of nature obliges every man to assist those whom he sees manifestly oppressed, when he can do it without danger and with hopes of success, much less ought he to be a hindrance to such as undertake their own defence.<239>
XXVIII. By following the principles here established, we may judge of the right of transporting merchandizes through the territories of another. This is also an imperfect right, and a duty of humanity, which obliges us to grant it to others; but the obligation is not rigorous, and the refusal cannot be a just reason for war.11
XXIX. Truly speaking, the laws of humanity indispensably oblige us to grant a passage to such foreign commodities as are absolutely necessary for life, which our neighbours cannot procure by themselves, and with which we are not able to furnish them. But, except in this case, we may have good reasons for hindering foreign commodities from passing through our country. Too great a resort of strangers is sometimes dangerous to a state; and besides, why should not a sovereign procure to his own subjects that profit, which would otherwise be made by foreigners, by means of the passage granted them?
XXX. It is not however contrary to humanity to require toll or custom for foreign commodities to which a passage is granted. This is a just reimbursement for the expences the sovereign is obliged to be at in repairing the high roads, bridges, harbours, &c.
XXXI. We must reason in the same manner in regard to commerce in general between different states. The same may be said of the right of being supplied with wives by our neighbours; a refusal on their side, though there be great plenty of women among them,12 does not authorize us to declare war.<240>
XXXII. We shall here subjoin something concerning wars undertaken on account of religion. The law of nature, which permits a man to defend his life, his substance, and all the other advantages which he enjoys, against the attacks of an unjust aggressor, certainly grants him the liberty also of defending himself against those who would, as it were by force, deprive him of his religion, by hindering him to profess that which he thinks the best, or by constraining him to embrace that which he thinks to be false.13
XXXIII. In a word, religion is one of the greatest blessings man can enjoy, and includes his most essential interests. Whoever opposes him in this respect, declares himself his enemy; and consequently he may justly use forcible methods to repel the injury, and to secure himself against the evil intended him. It is therefore lawful, and even just, to take up arms, when we are attacked for the cause of religion.14
XXXIV. But though we are allowed to defend ourselves in the cause of religion, we are not permitted to make war in order to propagate that which we profess, and to constrain those who have some principle or practice different from ours. The one is a necessary consequence of the other. It is not lawful to attack him who has a right to defend himself. If the defensive war is just, the offensive must needs be criminal. The very nature of religion does not permit that violent means should be used for its propagation; it consists in the internal persuasion. The right of mankind, in regard to the propagation of religion, is to inform and instruct those who are<241> in an error, and to use the soft and gentle methods of conviction. Men must be persuaded, and not compelled. To act otherwise, is to commit a robbery on them; a robbery so much the more criminal, as those who commit it endeavour to justify themselves by sacred authority. There is therefore no less folly, than impiety, in such a conduct.
XXXV. In particular, nothing is more contrary to the spirit of Christianity, than to employ the force of arms for the propagation of our holy religion. Christ, our divine master, instructed mankind, but never treated them with violence.15 The apostles followed his example; and the enumerations which St. Paul makes of the arms he employed for the conversion of mankind, is an excellent lesson to Christians.*
XXXVI. So far is a simple difference of opinion, in matters of religion, from being a just reason for pursuing, by force of arms, or disturbing in the least, those whom we think in an error; that, on the contrary, such as act in this manner, furnish others with a just reason of making war against them, and of defending those whom they unjustly oppress. Upon which occasion the following question occurs: Whether protestant princes may not, with a good conscience, enter into a confederacy to destroy the Inquisition, and oblige the powers, who suffer it in their dominions, to disarm that cabal, under which Christianity has so long groaned, and which, under a false pretence to zeal and piety, exercises a tyranny most horrible in itself,<242> and most contrary to human nature? Be that as it may, it is at least certain, that never would any hero have subdued monsters more furious and destructive to mankind, than he who could accomplish the design of purging the earth of these wicked men, who so impudently and cruelly abuse the specious shew of religion, only to procure wherewith to live in luxury and idleness, and to make both princes and subjects dependent on them.
XXXVII. These are the principal remarks which occur on the causes of war. To which let us add, that as we ought not to make war, which of itself is a very great evil, but to obtain a solid peace, it is absolutely necessary to consult the rules of prudence before we undertake it, however just it may otherwise appear. We must, above all things, exactly weigh the good or evil, which we may bring upon ourselves by it: For if in making war, there is reason to fear that we shall draw greater evils on ourselves, or those that belong to us, than the good we can propose from it; it is better to put up with the injury, than to expose ourselves to more considerable evils, than that for which we seek redress by arms.16
XXXVIII. In the circumstances here mentioned we may lawfully make war, not only for ourselves, but also for others; provided that he, in whose favour we engage, has just reason to take up arms, and that we are likewise under some particular tie or obligation to him, which authorises us to treat as enemies those who have done us no injury.17 <243>
XXXIX. Now among those, whom we may and ought to defend, we must give the first place to such as depend on the defender, that is, to the subjects of the state; for it is principally with this view of protection that men, before independent, incorporated themselves into civil society. Thus the Gibeonites having submitted themselves to the government of the Israelites, the latter took up arms on their account, under the command of Joshua. The Romans also proceeded in the same manner. But sovereigns in these cases ought to observe the maxim we have established in sect. 37. They ought to beware in taking up arms for some of their subjects, not to bring a greater inconveniency on the body of the state. The duty of the sovereign regards first and principally the interest of the whole, rather than that of a part; and the greater the part is, the nearer it approaches to the whole.18
XL. 2°. Next to subjects come our allies, whom we are expressly engaged by treaty to assist in time of need; and this, whether they have put themselves entirely under our protection, and so depend upon it; or whether assistance be agreed upon for mutual security.
XLI. But the war must be justly undertaken by our ally; for we cannot innocently engage to help any one in a war, which is manifestly unjust. Let us add here, that we may, even without prejudice to the treaty, defend our own subjects preferably to our allies, when there is no possibility of assisting<244> them both at the same time; for the engagements of a government to its subjects always supersede those into which it enters with strangers.
XLII. As to what Grotius says, that we are not obliged to assist an ally, when there is no hope of success; it is to be understood in this manner. If we see that our united forces are not sufficient to oppose the enemy, and that our ally, though able to treat with him on tolerable terms, is yet obstinately bent to expose himself to certain ruin; we are not obliged, by the treaty of alliance, to join with him in so extravagant and desperate an attempt. But then it is also to be considered, that alliances would become useless, if, in virtue of this union, we were not obliged to expose ourselves to some danger, or to sustain some loss in the defence of an ally.
XLIII. Here it may be enquired; when several of our allies want assistance, which ought to be helped first, and preferably to the rest? Grotius answers, that when two allies unjustly make war upon each other, we ought to succour neither of them; but if the cause of one ally be just, we must not only assist him against strangers, but also against another of our allies, unless there be some particular clause in a treaty, which does not permit us to defend the former against the latter, even though the latter has committed the injury. In fine, that if several of our allies enter into a league against a common foe, or make war separately against particular enemies, we must assist them all equally,<245> and according to treaty; but when there is no possibility of assisting them all at once, we must give the preference to the oldest confederate.19
XLIV. 3°. Friends, or those with whom we are united by particular ties of kindness and affection, hold the third rank. For though we have not promised them assistance, determined by a formal treaty; yet the nature of friendship itself implies a mutual engagement to help each other, so far as the stricter obligations the friends are under will permit; and the concern for each other’s safety ought to be much stronger, than that which is demanded by the simple connection of humanity.20
XLV. I say that we may take up arms for our friends, who are engaged in a just war; for we are not under a strict obligation to assist them: and this condition ought to be understood, if we can do it easily, and without any great inconveniency to ourselves.
XLVI. 4°. In fine, we may affirm that the single relation, in which all mankind stand to each other, in consequence of their common nature and society, and which forms the most extensive connection, is sufficient to authorise us in assisting those who are unjustly oppressed; at least if the injustice be considerable, and manifest, and the party injured call us to his assistance; so that we act rather in his name, than in our own. But even here we must make this remark, that we have a right to succour the distressed purely from humanity, but that<246> we are not under a strict obligation of doing it. It is a duty of imperfect obligation, which binds us only so far as we can practise it, without bringing a considerable inconveniency upon ourselves; for all circumstances being equal, we may, and even ought to prefer our own preservation to that of another.
XLVII. It is another question, whether we can undertake a war in defence of the subjects of a foreign prince, against his invasions and oppressions, merely from the principle of humanity? I answer, that this is permitted only in cases where the tyranny is risen to such a height, that the subjects themselves may lawfully take up arms, to shake off the yoke of the tyrant, according to the principles already established.21
XLVIII. It is true, that since the institution of civil societies, the sovereign has acquired a peculiar right over his subjects, in virtue of which he can punish them, and no other power has any business to interfere. But it is no less certain, that this right hath its bounds, and that it cannot be lawfully exercised, except when the subjects are really culpable, or at least when their innocence is dubious. Then the presumption ought to be in favour of the sovereign, and a foreign power has no right to intermeddle with what passes in another state.
XLIX. But if the tyranny be arrived at its greatest height, if the oppression be manifest, as when a<247> Busiris or Phalaris oppress their subjects in so cruel a manner, as must be condemned by every reasonable man living; we cannot refuse the subjects, thus oppressed, the protection of the laws of society. Every man, as such, has a right to claim the assistance of other men when he is really in necessity; and every one is obliged to give it him, when he can, by the laws of humanity. Now it is certain, that we neither do, nor can renounce those laws, by entering into society, which could never have been established to the prejudice of human nature: though we may be justly supposed to have engaged, not to implore a foreign aid for slight injuries, or even for great ones, which affect only a few persons.
But when all the subjects, or a considerable part of them, groan under the oppression of a tyrant, the subjects, on the one hand, re-enter into the several rights of natural liberty, which authorises them to seek assistance wherever they can find it; and, on the other hand, those who are in a condition of giving it them, without any considerable damage to themselves, not only may, but ought to do all they can to deliver the oppressed; for the single consideration of pity and humanity.22
L. It appears indeed, from ancient and modern history, that the desire of invading the states of others is often covered by those pretexts; but the bad use of a thing, does not hinder it from being just. Pirates navigate the seas, and robbers wear swords, as well as other people.<248>
[1. ]This paragraph and the next draw on DGP II.1 §1 and DGP II.22 §2.
[2. ]The summary of Grotius’s position presented in this and the four following paragraphs is taken from DNG VIII.6 §4 note 1.
[* ]See the explication of these principles in Budeus’s Jurisprud. hist. specim. § 28, &c.
[3. ]Based on DGP II.22 §5.
[4. ]Based on DGP II.22 §6 note 1.
[5. ]This paragraph draws on DGP II.22 §§8–10.
[6. ]This is drawn from DGP II.22 §12, where Grotius also denies that there are men who are slaves by nature.
[7. ]See DNG VIII.6 §3 note 2.
[8. ]Grotius discussed granting passage in DGP II.2 §13, which Burlamaqui makes use of here. Burlamaqui uses Pufendorf ’s criticism of Grotius in DNG III.3 §5 and especially Barbeyrac’s equally critical remarks in DGP II.2 §13 note 1 to work out his own account as it is laid out in this and the four following paragraphs.
[9. ]This paragraph and the two following are drawn from DNG III.3 §5 note 7.
[* ]See Just. lib. iv. cap. 4. & 8. and Liv. lib. vii. cap. 38.
[10. ]Based on DNG III.3 §5.
[11. ]This and the following paragraphs are based on DNG III.3 §6.
[12. ]The translator adds “though there be great plenty of women among them.” This paragraph is from DNG III.3 §§13–14, while the preceding paragraph provided an abbreviated overview of DNG III.3 §7.
[13. ]This paragraph elaborates on DNG VIII.6 §3 note 1.
[14. ]This paragraph draws on DNG VII.8 §5 note 7, while the following summarizes Grotius’s statements on wars of religion; Burlamaqui could be using Barbeyrac’s summary in DNG VIII.6 §3 note 1. See also DNG VII.4 §11 note 2.
[15. ]Grotius makes a similar statement in DGP II.20 §48, a statement that Barbeyrac summarizes in DNG VIII.6 §3 note 1, which seems to be Burlamaqui’s main source here. Barbeyrac makes similar claims in Traité de la morale des pères §29, where he also adds the reference to the Pauline letters to the Romans that Burlamaqui uses here. The next paragraph repeats Barbeyrac’s standpoint in DNG VIII.6 §3 note 1.
[* ]2 Cor. chap. vi. v. 4, &c. and chap. x. v. 4.
[16. ]This forms a summary of DGP II.24.
[17. ]Taken from DNG VIII.6 §14, a paragraph that summarizes DGP II.25, especially §4.
[18. ]Based on DNG VIII.6 §14, except for the example which is from the passages in Grotius that the DNG paragraph summarizes, DGP II.25 §§1–2. The next two paragraphs are from the same paragraph in the DNG, or of DGP II.25 §4.
[19. ]This paragraph is from DNG VIII.9 §5 note 1.
[20. ]This and the two following paragraphs are again from DNG VIII.6 §14, except that Burlamaqui is less critical of a right of interference than Pufendorf.
[21. ]This paragraph is taken either from DNG VIII.6 §14 or from DGP II.25 §8, but the next paragraph is clearly from the latter.
[22. ]Read: “… for the single reason that they are men and members of the human society that civil societies participate in.” This paragraph is from DGP II.25 §8 note 1. The next paragraph is again from the main text of that paragraph.