§ 2. It is often maintained that the Law of Nations is concerned with legal differences only, political differences being a matter not of law but of politics. Now it is certainly true that only legal differences can be settled by a juristic decision of the underlying juristic question, whatever may be the way in which such decision is arrived at. But although political differences cannot be the objects of juristic decision, they can be settled short of war by amicable or compulsive means. And legal differences, although within the scope of juristic decision, can be of such kinds as to prevent the parties from submitting them to such decision, without being of a nature that they cannot be settled peaceably at all. Moreover, although the distinction between legal and political differences is certainly correct in theory and of importance in practice, nevertheless, in practice, a sharp line frequently cannot be drawn, as has just been pointed out. Therefore the Law of Nations is not exclusively concerned with legal differences, for in fact all amicable means of settling legal differences are likewise means of settling political differences, and so are two of the compulsive means of settling differences--namely, pacific blockade and intervention. [Sidenote: Amicable in contradistinction to compulsive settlement of Differences.] § 3. Political and legal differences can be settled either by amicable or by compulsive means. There are four kinds of amicable means--namely, negotiation between the parties, good offices of third parties, mediation, and arbitration.[2] And there are also four kinds of compulsive means--namely, retorsion, reprisals (including embargo), blockade, and intervention of third States. No State is allowed to make use of compulsive means before negotiation has been tried, but there is no necessity for the good offices or mediation of third States, and eventually arbitration,[3] to be tried beforehand also. Frequently, however, States nowadays make use of the so-called Compromise Clause[4] in their treaties, stipulating thereby that any differences arising between the contracting parties with regard to matters regulated by, or to the interpretation of, the respective treaties shall be settled through the amicable means of arbitration to the exclusion of all compulsive means. And there are even a few examples of States which have concluded treaties stipulating that all differences, without exception, that might arise between them should be amicably settled by arbitration.[5] These exceptions, however, only confirm the rule that no international legal duty exists for States to settle their differences amicably through arbitration, or even to try to settle them in this way, before they make use of compulsive means.