David Hume

“ 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. ”

“ When civil government has been establish'd over the greatest part of mankind, and different societies have been form'd 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 consider'd as one person ”

“ This obligation of interest rests not 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 ”

“ But here we may observe, that tho' the intercourse of different states be advantageous, and even sometimes necessary, yet it is not so necessary nor advantageous as that among individuals, without which 'tis 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 mural obligation, which arises from it, must partake of its weakness ”

“ But tho' 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 poison'd arms, with other duties of that kind, which are evidently calculated for the commerce, that is peculiar to different societies. ”

“ There is a maxim very current in the world, which few politicians are willing to avow, but which has been authoriz'd by the practice of all ages, that there is a system of morals calculated for princes, much more free than that which ought to govern private persons. 'Tis 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 ”