But, says Monsieur Wolf, a rigid adherence to the law of nature cannot always prevail in that commerce and society of nations; it must undergo various modifications, which can only be deduced from this idea of a kind of great republic of nations, whose laws, dictated by sound reason and founded on necessity, shall regulate the alterations to be made in the natural and necessary law of nations, as the civil laws of a particular state determine what modifications shall take place in the natural law of individuals. I do not perceive the necessity of this consequence; and I flatter myself that I shall, in the course of this work, be able to prove, that all the modifications, all the restrictions,—in a word, all the alterations which the rigour of the natural law must be made to undergo in the affairs of nations, and from which the voluntary law of nations is formed,—to prove, I say, that all these alterations are deducible from the natural liberty of nations, from the attention due to their common safety, from the nature of their mutual correspondence, their reciprocal duties, and the distinctions of their various rights, internal and external, perfect and imperfect,—by a mode of reasoning nearly similar to that which Mon-<xvi>sieur Wolf has pursued, with respect to individuals, in his treatise on the law of nature.
In that treatise it is made to appear that the rules, which, in consequence of the natural liberty of mankind, must be admitted in questions of external right do not cancel the obligation which the internal right imposes on the conscience of each individual. It is easy to apply this doctrine to nations, and—by carefully drawing the line of distinction between the internal and the external right—between the necessary and the voluntary law of nations—to teach them not to indulge themselves in the commission of every act which they may do with impunity, unless it be approved by the immutable laws of justice, and the voice of conscience.
Since nations, in their transactions with each other, are equally bound to admit those exceptions to, and those modifications of, the rigour of the necessary law, whether they be deduced from the idea of a great republic of which all nations are supposed to be the members, or derived from the sources whence I propose to draw them,—there can be no reason why the system which thence results, should not be called the Voluntary Law of nations, in contradistinction to the necessary, internal, and consciential law. Names are of very little consequence: but it is of considerable importance carefully to distinguish these two kinds of law, in order that we may never confound what is just and good in itself, with what is only tolerated through necessity.
The necessary and the voluntary law of nations are therefore both established by nature, but each in a different manner; the former as a sacred law which nations and sovereigns are bound to respect and follow in all their actions; the latter, as a rule which the general welfare and safety oblige them to admit in their transactions with each other. The necessary law immediately proceeds from nature; and that common mother of mankind recommends the obser-<xvii>vance of the voluntary law of nations, in consideration of the state in which nations stand with respect to each other, and for the advantage of their affairs. This double law, founded on certain and invariable principles, is susceptible of demonstration, and will constitute the principal subject of this work.
There is another kind of law of nations, which authors call arbitrary, because it proceeds from the will or consent of nations. States, as well as individuals, may acquire rights and contract obligations, by express engagements, by compacts and treaties: hence results a conventional law of nations, peculiar to the contracting powers. Nations may also bind themselves by their tacit consent: upon this ground rest all those regulations which custom has introduced between different states, and which constitute the usage of nations, or the law of nations founded on custom. It is evident that this law cannot impose any obligation except on those particular nations who have, by long use, given their sanction to its maxims: it is a peculiar law, and limited in its operation, as the conventional law: both the one and the other derive all their obligatory force from that maxim of the natural law which makes it the duty of nations to fulfil their engagements, whether express or tacit. The same maxim ought to regulate the conduct of states with regard to the treaties they conclude, and the customs they adopt. I must content myself with simply laying down the general rules and principles which the law of nature furnishes for the direction of sovereigns in this respect. A particular detail of the various treaties and customs of different states belongs to history, and not to a systematic treatise on the law of nations.
Such a treatise ought, as we have already observed, principally to consist in a judicious and rational application of the principles of the law of nature to the affairs and conduct of nations and sovereigns. The study of the law of nations supposes therefore a pre-<xviii>vious knowledge of the ordinary law of nature: and in fact I proceed on the supposition that my readers are already, to a certain degree at least, possessed of that knowledge. Nevertheless, as it is not agreeable to readers in general to be obliged to recur to other