When civil government has been established over the greatest part of mankind, and different societies have been formed contiguous to each other, there arises a new set of duties among the neighbouring states, suitable to the nature of that commerce, which they carry on with each other. Political writers tell us, that in every kind of intercourse, a body politic is to be considered as one person; and indeed this assertion is so far just, that different nations, as well as private persons, require mutual assistance; at the same time that their selfishness and ambition are perpetual sources of war and discord. But though nations in this particular resemble individuals, yet as they are very different in other respects, no wonder they regulate themselves by different maxims, and give rise to a new set of rules, which we call the laws of nations. Under this head we may comprize the sacredness of the persons of ambassadors, the declaration of war, the abstaining from poisoned arms, with other duties of that kind, which are evidently calculated for the commerce, that is peculiar to different societies.

But though these rules be super-added to the laws of nature, the former do not entirely abolish the latter; and one may safely affirm, that the three fundamental rules of justice, the stability of possession, its transference by consent, and the performance of promises, are duties of princes, as well as of subjects. The same interest produces the same effect in both cases. Where possession has no stability, there must be perpetual war. Where property is not transferred by consent, there can be no commerce. Where promises are not observed, there can be no leagues nor alliances. The advantages, therefore, of peace, commerce, and mutual succour, make us extend to different kingdoms the same notions of justice, which take place among individuals.

There is a maxim very current in the world, which few politicians are willing to avow, but which has been authorized by the practice of all ages, that there is a system of morals cakulated for princes, much more free than that which ought to govern private parsons. It is evident this is not to be understood of the lesser extent of public duties and obligations; nor will any one be so extravagant as to assert, that the most solemn treaties ought to have no force among princes. For as princes do actually form treaties among themselves, they must propose some advantage from the execution of them; and the prospect of such advantage for the future must engage them to perform their part, and must establish that law of nature. The meaning, therefore, of this political maxim is, that though the morality of princes has the same extent, yet it has not the same force as that of private persons, and may lawfully be trangressed from a more trivial motive. However shocking such a proposition may appear to certain philosophers, it will be easy to defend it upon those principles, by which we have accounted for the origin of justice and equity.

When men have found by experience, that it is impossible to subsist without society, and that it is impossible to maintain society, while they give free course to their appetites; so urgent an interest quickly restrains their actions, and imposes an obligation to observe those rules, which we call the laws of justice. This obligation of interest rests nor here; but by the necessary course of the passions and sentiments, gives rise to the moral obligation of duty; while we approve of such actions as tend to the peace of society, and disapprove of such as tend to its disturbance. The same natural obligation of interest takes place among independent kingdoms, and gives rise to the same morality; so that no one of ever so corrupt morals will approve of a prince, who voluntarily, and of his own accord, breaks his word, or violates any treaty. But here we may observe, that though the intercourse of different states be advantageous, and even sometimes necessary, yet it is nor so necessary nor advantageous as that among individuals, without which it is utterly impossible for human nature ever to subsist. Since, therefore, the natural obligation to justice, among different states, is not so strong as among individuals, the moral obligation, which arises from it, must partake of its weakness; and we must necessarily give a greater indulgence to a prince or minister, who deceives another; than to a private gentleman, who breaks his word of honour.

Should it be asked, what proportion these two species of morality bear to each other? I would answer, that this is a question, to which we can never give any precise answer; nor is it possible to reduce to numbers the proportion, which we ought to fix betwixt them. One may safely affirm, that this proportion finds itself, without any art or study of men; as we may observe on many other occasions. The practice of the world goes farther in teaching us the degrees of our duty, than the most subtile philosophy, which was ever yet invented. And this may serve as a convincing proof, that all men have an implicit notion of the foundation of those moral rules concerning natural and civil justice, and are sensible, that they arise merely from human conventions, and from the interest, which we have in the preservation of peace and order. For otherwise the diminution of the interest would never produce a relaxation of the morality, and reconcile us more easily to any transgression of justice among princes and republics, than in the private commerce of one subject with another.