XIII. and XIV. There are two cases, in which a person may not perform his engagement or promise, without being guilty of treachery: and those are, where the conditions have not been fulfilled, or some compensation has been made. For in one and the same treaty all the clauses seem connected with each other, as a kind of condition expressing the intention of one party to fulfil his engagement, if the other shall do the same. Therefore Tullus, in replying to the Albans invokes destruction upon the head of that people who first rejected the just claims of ambassadors demanding restitution, wishing that all the calamities of war might fall upon them. For, says Ulpian, he shall no longer be held as a confederate, who has renounced a treaty, owing to some condition, on which it was made, not being fulfilled. For which reason, wherever it is intended otherwise, it is usually stated in express terms, that the violation of any particular clause shall not annul the whole treaty.
XV. The origin of compensation was explained in the second book of this treatise,[75] where it was said to be the power and right of receiving an equivalent, for some thing belonging to us, which is in the hands of another, or any thing due to us, which we cannot otherwise obtain: and much more then have we a right on the same account to detain any thing which is ALREADY IN OUR POWER, whether it be of a corporeal or an incorporeal kind. So that we are not obliged to perform a promise, if it be no more than equivalent to a thing of ours which the other party detains. Seneca, in his sixth book On Benefits, says that a creditor often becomes under an obligation to his debtor, if he takes more than an equivalent for his debt. For though it may be granted that he has lent money, yet if by such a loan he has obtained the possession of lands, which he never bought, he changes situations with his debtor, and becomes a debtor in his turn.
XVI. It will be the same, if one of the contracting parties owes as much, or more, from some other engagement: and the debt cannot otherwise be obtained, than by taking advantage of the present contract, though it has no connection with the former debt. But in a LEGAL point of view, all actions are perfectly distinct, nor can their forms, their grounds, or their substance be confounded; but certain cases are confined to certain laws, to which it is necessary invariably to adhere: one law cannot be mixed with another, but every one in the prosecution of a right must tread upon invariable and beaten ground. But the law of nations does not regard such distinctions, it allows us to transgress them where there is no other means of obtaining our right.
XVII. and XVIII. The same may be said too, where the party exacting a promise, has not contracted any debt by engagement, but has done an injury to the promiser. And whatever is due by way of punishment may be balanced against a promise.
XIX. If while a law-suit is depending, the parties enter into an agreement of any kind, either to pay the costs, or to make good other damages, they cannot avail themselves both of this agreement, and claim a further compensation for the original matter in dispute. In the same manner, if during the continuance of a war the belligerents negotiate for a conclusion of the original dispute, they are supposed thereby to settle every cause of hostility, nor can they any further avail themselves of the rights of war, so as to enjoy both the advantages of them, and of negotiation, at the same time. For if this were the case, no treaties could ever be enforced with certainty.
It may be asked, of what nature are the things for which a promise of compensation should be given? In answer to which it may be observed, that such a promise or engagement may be made in lieu of some other obligation incurred during the course of a war: as for instance, where the breach of a truce has been committed, the rights of an ambassador violated, or any other action done, repugnant to the principles established by the law of nations among belligerent powers.
Still it must be observed that the parties, in making compensation, should abstain with the utmost caution from infringing upon the rights of a third person, especially where this can be done without abandoning the principles of the law of nations, which makes the effects of subjects answerable for the debts of the state. Besides it is the mark of a dignified mind to adhere to engagements even after receiving an injury. On which account the Indian sage Jarchas commended that king, who on sustaining an injury from a neighbouring and confederate power, said he should not think himself released from his sworn engagements, which were solemn acts, that no injustice on the part of another could repeal.
Almost all questions relating to pledges of faith given by one belligerent power to another, may be solved upon the principles before laid down, in explaining the nature and force of promises in general; of oaths, treaties, and conventions, and also in explaining the rights of the obligations of kings, and the method of interpreting doubtful points. But in order to remove every doubt and difficulty, perhaps a brief discussion of the most usual and practical topics of negotiation will not be deemed tedious.