In the latter portion of the last lecture I endeavoured to establish threepropositionswhich I hold to be extremely important to the intelligent studyof International LawThe first of them was that the process by which InternationalLaw obtained authority in a great part of Europe was a late st age of theprocess by which the Roman Law had also obtained authority over very muchthe saline part of the worldNextI said that this process had little orno analogy to what is now understood by legislationbut consisted in thereception of a body of doctrine in a mass by specially constituted or trainedmindsLastlyI contended that this doctrineso spread over Europeconsistedmainly of that part of the Roman Law which the Romans themselves had calledJus Gentium or Jus Naturae -Law of Nationsor Law of Natureterms whichhad become practicably convertible.
The inquiry into the exact meaning of the phrase 'Law of Naturebelongsto a different department of juridical studyand I think it will be sufficientif I briefly summarise the viewsthemselves considerably condensedwhichI published some years ago in a volume from which I quoted in the last lecture.
Jus Gentiumor Law of Nationshad notso I thoughtmuch colour at firstof the meaning which it afterwards acquiredIt was probablyI saidhalfas a measure of policeand half in furtherance of commercethat jurisdictionwas first assumed in disputes in which either foreignersor a native anda foreignerwere concernedIn order to obtain some principles upon whichthe questions to be adjudicated on could be settledthe Roman praetor peregrinusresorted to the expedient of selecting the rules of law common to Rome andto the different Italian communities in which the immigrants were bornInother wordshe set himself to form a system answering to the primitive andliteral meaning of Jus Gentiumthat is law common to all nationsJus Gentiumwas in fact the sum of the common ingredients in the customs of the old ItaliantribesIt was accordingly a collection of rules and principles determinedby observation to be common to the institutions which prevailed among thevarious Italian racesNowit is to be remembered that every Roman of positionwho followed public life was in the course of his official career not only,so far as his powers wenta statesmanbut specially a general and a judge.
Speculation upon legal principles manifestly became common among the Romanaristocracyand in course of time the question suggested itself what wasthe essential nature of this Jus Gentium which had at first very possiblybeen regarded as a mere market lawThe answer was shaped by the Greek philosophy,which was a favourite subject of study among the class to which the Romanlawyers belongedSeen in the light of Stoical doctrine the Law of Nationscame to be identified with the Law of Naturethat is to saywith a numberof supposed principles of conduct which man in society obeys simply becausehe is manThus the Law of Nature is simply the Law of Nations seen in thelight of a peculiar theoryA passage in the Roman Institutes shows thatthe expressions were practically convertibleThe greatest function of theLaw of Nature was discharged in giving birth to modern International Lawand the modern Law of War.
I ought to observe that in this account of the matter probably one correctionhas to be madeSome acute scholars have examined the authorities since Iwroteand they are inclined to think that very anciently there are someinstances of the use of Jus Gentium in a wider and something like its modernsensethat islaw binding on tribes and nations as suchGranting thatthis is sostill the impression that the Roman Law contained a system ofwhat would now be called International Lawand that this system was identicalwith the Law of Naturehad undoubtedly much influence in causing the rulesof what the Romans called Natural Law to be engrafted onand identifiedwiththe modern law of nationsWhen the older Roman sense of the wordsdied out cannot be confidently ascertainedthough of course in a world whichwas divided between two great rival sovereignsthe Roman Emperor and theKing of Persiathere was little room for Law of Nations in the true senseof the words.
Whenhoweverat what perioddid this Jus Gentium or Jus Natural riseinto the dignity which the Roman lawyers give to itThere is a strong probabilitythat this exaltation was not very ancientbut that it took place duringthe periodroughly about three hundred yearscovered by the so-called RomanPeaceThat Peace extended from the time at which the Roman Empire was settledby the success of Augustus over all his enemies to the early years of thethird centuryThe Roman Law transformed a large number of the ideas of agreat portion of the worldbut its own transformation from a technical toa plastic system was one of the results of the so-called Roman PeaceIfwe want to know what war iswe should study what peace isand see whatthe human mind is when it is unaffected by warWe should study the KoreanPeaceduring which the existing legal conception of the relation of thesexes framed itselfduring which the Christian Church was organisedandduring which the old Law of Nations or Nature transformed itself into anideal system specially distinguished by simplicity and symmetryand becamea standard for the legal institutions of all systems of jurisprudence.
