The most superficial student of Roman history must be struckby the extraordinary degree in which the fortunes of the republicwere affected by the presence of foreigners, under differentnames, on her soil. The causes of this immigration arediscernible enough at a later period, for we can readilyunderstand why men of all races should flock to the mistress ofthe world; but the same phenomenon of a large population offoreigners and denizens meets us in the very earliest records ofthe Roman State. No doubt, the instability of society in ancientItaly, composed as it was in great measure of robber tribes, gavemen considerable inducement to locate themselves in the territoryof any community strong enough to protect itself and them fromexternal attack, even though protection should be purchased atthe cost of heavy taxation, political disfranchisement, and muchsocial humiliation. It is probable, however, that thisexplanation is imperfect, and that it could only be completed bytaking into account those active commercial relations which,though they are little reflected in the military traditions ofthe republic, Rome appears certainly to have had with Carthageand with the interior of Italy in pre-historic times. Whateverwere the circumstances to which it was attributable, the foreignelement in the commonwealth determined the whole course of itshistory, which, at all its stages, is little more than anarrative of conflicts between a stubborn nationality and analien population. Nothing like this has been seen in moderntimes; on the one hand, because modern European communities haveseldom or never received any accession of foreign immigrantswhich was large enough to make itself felt by the bulk of thenative citizens, and on the other, because modern states, beingheld together by allegiance to a king or political superior,absorb considerable bodies of immigrant settlers with a quicknessunknown to the ancient world, where the original citizens of acommonwealth always believed themselves to be united by kinshipin blood, and resented a claim to equality of privilege as ausurpation of their birthright. In the early Roman republic theprinciple of the absolute exclusion of foreigners pervaded theCivil Law no less than the Constitution. The alien or denizencould have no share in any institution supposed to be coeval withthe State. He could not have the benefit of Quiritarian law. Hecould not be a party to the nexum which was at once theconveyance and the contract of the primitive Romans. He could notsue by the Sacramental Action, a mode of litigation of which theorigin mounts up to the very infancy of civilisation. Still,neither the interest nor the security of Rome permitted him to bequite outlawed. All ancient communities ran the risk of beingoverthrown by a very slight disturbance of equilibrium, and themere instinct of self-preservation would force the Romans todevise some method of adjusting the rights and duties offoreigners, who might otherwise-and this was a danger of realimportance in the ancient world -- have decided theircontroversies by armed strife. Moreover, at no period of Romanhistory was foreign trade entirely neglected. It was thereforeprobably half as a measure of police and half in furtherance ofcommerce that jurisdiction was first assumed in disputes to whichthe parties were either foreigners or a native and a foreigner.
The assumption of such a jurisdiction brought with it theimmediate necessity of discovering some principles on which thequestions to be adjudicated upon could be settled, and theprinciples applied to this object by the Roman lawyers wereeminently characteristic of the time. They refused, as I havesaid before, to decide the new Cases by pure Roman Civil Law.
They refused, no doubt because it seemed to involve some kind ofdegradation, to apply the law of the particular State from whichthe foreign litigant came. The expedient to which they resortedwas that of selecting the rules of law common to Rome and to thedifferent Italian communities in which the immigrants were born.
In other words, they set themselves to form a system answering tothe primitive and literal meaning of Jus Gentium, that is, Lawcommon to all Nations. Jus Gentium was, in fact, the sum of thecommon ingredients in the customs of the old Italian tribes, forthey were all the nations whom the Romans had the means ofobserving, and who sent successive swarms of immigrants to Romansoil. Whenever a particular usage was seen to be practised by alarge number of separate races in common it was set down as partof the Law common to all Nations, or Jus Gentium. Thus, althoughthe conveyance of property was certainly accompanied by verydifferent forms in the different commonwealths surrounding Rome,the actual transfer, tradition, or delivery of the articleintended to be conveyed was a part of the ceremonial in all ofthem. It was, for instance, a part, though a subordinate part, inthe Mancipation or conveyance peculiar to Rome. Tradition,therefore, being in all probability the only common ingredient inthe modes of conveyance which the jurisconsults had the means ofobserving, was set down as an institution Juris Gentium, or ruleof the Law common to all Nations. A vast number of otherobservances were scrutinised with the same result. Some commoncharacteristic was discovered in all of them, which had a commonobject, and this characteristic was classed in the Jus Gentium.
The Jus Gentium was accordingly a collection of rules andprinciples, determined by observation to be common to theinstitutions which prevailed among the various Italian tribes.
