Jus, law, right, equity, authority, and rule.
A Roman 'magistratus' generally did not investigate the facts in dispute in such matters as were brought before him; he appointed a judex for that purpose, and gave him instructions. Accordingly, the whole procedure was expressed by the two phrases Jus and Judicium; of which the former comprehended all that took place before the magistratus (in jure), and the latter all that took place before the judex (in judicio). Originally, even the magistratus was called judex, as, for instance, the consul and pr'tor (Liv. iii. 55); and under the empire the term 'judex' often designated the pr'ses, Smith's Dict. of Antiq.
All law jus) is distributed into two parts--Jus Gentium and Jus Civile--and the whole body of law peculiar to any state is its Jus Civile (Cic. De Orat. I. 44). The Roman Law, therefore, which is peculiar to the Roman state, is its Jus Civile, sometimes called Jus Civile Romanorum, but more frequently designated by the term Jus Civile only, by which is meant the Jus Civile of the Romans.
The Jus Gentium is viewed by Gaius as springing out of the Naturalis Ratio, common to all mankind, which is still more clearly expressed in another passage (i. 89), where he uses the expression 'omnium civitatum jus' as equivalent to the Jus Gentium, and as founded on the Naturalis Ratio.
The Naturale Jus and the Jus Gentium are therefore identical. Cicero (Off. iii. 5) opposes Natura to Leges, where he explains Natura by the term Jus Gentium, and makes Leges equivalent to Jus Civile.
In the partitiones (c. 37) he also divides Jus into Natura and Lex.
There is a threefold division of Jus made by Ulpian and others, which is as follows: --Jus Civile; Jus Gentium, or that which is common to all mankind; and Jus Naturale, which is common to man and beasts. The foundation of this division seems to have been a theory of the progress of mankind from what is commonly termed a state of nature; first, to a state of society, and then to a condition of independent states. This division had, however, no practical application, and must be viewed merely as a curious theory, except so far as positive law, which may be said to be the expression of speciali-zed requirements traceable to natural instincts, is a development of Ulpian's Jus Naturale.
Another division is referred to and sometimes expressed by the words Jus and Fas (fas et jura sinunt, Virg. Georg. I. 269), the law of things not pertaining to religion, and of things pertaining to it; also respectively opposed to one another by the terms Res Juris Humani et Divini (Instit. Ii. tit. 1). As the components of a single generalization, 'juris-prudential.'
The terms Jus Scriptum and Non Scriptum, as explained in the Institutes (i. tit. 2), comprehended the whole of the Jus Civile; for it was all either Scriptum or Non Scriptum, whatever other divi-sions there might be (Ulp. Dig. 1, tit. 1, s. 6). Jus Scriptum comprehended everything, except that 'quod usus approbavit.' This division of Jus Scriptum and Non Scriptum does not appear in Genius. It was borrowed from the Greek writers, and seems to have little or no practical application among the Romans.
There is another division of the matter of law which appears among the Roman jurists, viz., the Law of Persons, which is expressed by the phrase (1) 'jus quod ad personas pertinet,' (2) 'vel ad re' (the Law of Things), and (3) 'vel ad actione' (the Law of Procedure) (Gaius, i. 8), Cf. Smith's Dict. of Antiq.
Jus constitui oportet inhis qu' ut plurinum accidunt non qu' ex inopinato. D. 1, 3, 3.--(Law ought to be made with a view to those cases which happen most frequently, and not to those which are of rare or accidental occurrence.)