NATURALIZATION. !78 ■ NATURAL LAW. (New York. IriUDi; lUii'nd sinliitcs of the United Utates, title "Naturalization ;" ami Moore, Diyest of International Law (Washing- ton, 1903). See Alie.v; Allegiance; Citizen. NATURALIZATION, lu biology, the estab- lishmcMit of jilaiils and animals in a niw region, especially through the agency of man. rrimarily, e.otic species soon become feral and compete with indigenous species. They frequently never gain a foothold, but if they do they usually spread at first with extraordinary vigor, owing to the ab- sence of their natural enemies. But later an ad- justment with the other species in the country occurs, and after that the disproportionate num- bers of the introduced form disappear, i.e. the new species becomes adjusted or 'naturalized.' Compare Accluiatization. NATURAL LAW. Greek Piiii.osopiiy. Some of the Orcck ^^ophists, and later the Epicureans, held that law and justice were arbitrary con- ventions established by the weak for self-defense against the natural right of the strong. Socrates, in this as in other matters, antagonized the theories of the Sophists; but it was Aristotle who fornuilated the conception of natural justice which has remained dominant to the present day. In his view justice is in part legal, in part natural. Legal justice deals with matters which must 1)0 regulated, but which may be variously regulated. Natural justice, on the other hnn<l, is not arbitrary; its rules are everywhere similar. The Stoics went further: they asserted that the rules of natural justice w'ere founded on reason, and were therefore discernible by reason ; and the later Stoics termed this rational order nat- ural law. KoMAN .TrRisPEUDENCE. The Roman lawyers noted the fact that many substantially identical rules were observed by all the ilediterranean nations; and to this common law they gave the name 'law of nations' (/».s ijentium) . In the first e<'ntury before Christ they began to speak of 'natural law.' In the Roman juristic litera- ture the terra is used in four different senses: (1) Natural law is identified with universal law (jus gentium). This is practically the Aris- totelian sense. ('2) Natural law is contrasted with the law observed by all nations; e.g. it is said that by natire all men arc free, and that slavery has been introduced by the law of nations. This is the Stoic conception of natural law. (3) Sporadically, the Kpieurean idea ap|iears, as when it is said that buyers and sellers have a niitural right to overreach one another as regards price. (4) Ulpian has a theory which seems to have been peculiarly his own. but to which .lustinian gave a factitious importance by in- cluding in his Institutes Ulpian's definition: "Natural law is that which nature has taught all living things." 'Hie illustrations, which refer to rudimentary family life, are biological rather than legal. Although the Roman jurists re- ferred to the law of nature fur the interpretation of their own law, and even drew from it sup- plementary rules where their own law was silent, they referred far more frequently, and for the same purposes, to 'natural reason' and to 'equity;' and they never ascriliod to the laW of nature such authority as to question the validity of 11 Roman ruli' because it was not in accordance with natural law. Sec CmL Law; Jus Gen- TlfM ; .lus Natub.e. ^Iem.eval TiiEoi:ii;s. The doctrines of Aris- totle and of the Itonian jurisprudence were gen- erally accepted in the Midille Ages as authori- tative, and man}' attempts were made to reconcile them. There was a marked tendency to identify natural law with the law of God: in the Decretum of (Jratiau it is declared that natural law is identical with the Golden Rule. Thomas .quinas divided all law into four classes: elermil, divine, natural, and human. The eternal law is the controlling plan of the univer.-<e, existing in the mind of God. A part of this eternal law has been directly revealed to men; this is tlu; divine law. Another part is discerned by human rea- son; this is natural law. Except in its funda- mental principles, natural law is not imnuUable, for "it seems to be natural to the human reason that it comes gradually from the im]ierfect to the perfect." Human law is the application uf nat- ural law to particular conditions. The practical inlluenee of these theories ujxui the development of European law during the Middle Ages was slight. In the development of the English com- mon law, as in the development of the Roman Imperial law, appeals to natural reason were far more frequent than appeals to natural law. In England, however, as well as on the Continent, the general law merchant, which was jus ycnliuni in the Roman sense, was recognized as natural law. Modern Theories. Natural Law as a Factor IN Legal Reforms. The general elVeet of the Protestant Reformation was to free the concep- tion of natural law from ecclesiastical associa- tions and limitations, and to rcenipliasize it» rational character. Natural-law theories became etfective factors in the reform of the law. In the seventeenth century natur:il law was treated as a source of international law; and many rules which had not yet become rules of inli'rnationnl custom attained this positioii Ihrougii the writ- ings of Grotius, Pufendorf. and others on 'the law of nature and of nations.' Later, during the eighteenth century and the earlier years of the nineteenth, when the groat national codes of civil and criminal law were drawn up in Prussin, Austria. Prance, and other countries, natural-law theories helped to give the legislators n more independent attitude toward established law and custom. In England utilitarianism played a similar jiart in facilitating hiw reform. Xatiual KiciiiTS as tmk Masis m- Politic.vl Revolution. The theory of Cicero and of Thomas Aquinas, that laws in conlliet with natural law are not truly laws, developed its revolutionary (not to say anarchistic) possibilities when the in- terpretation of natural law passed from secular and ecclesiastical authorities to the people at large. The theory that the popular consciousness is the true inter])rcter of that n:itiiiMl law by which all rulers are bound, found freipient ex- pression before the close of the .Middle .ges;. e.g. in (he writings of Marsiulio of I'adua. W ith the Protestant Reformation these theories became practical forces in matters religious ami political, and the tendencies which they represented first obtained a tcmiiorary triumph in England under the Commonwealth. Those legal rights which Englishmen had succeeded, through centuries of conlliet. in asserting against the Crown were brought by the Levelers into connection with the natural-law theories of the Continent, and thenceforth the rights of the individual to life.
