The change from republic to empire did not immediately make any difference, and the praetors continued to issue their edicts (though we may doubt whether they ever made changes without imperial or senatorial authority), but in the long run their wide powers were evidently felt to be inconsistent with the emperor's supremacy. Hadrian consequently, in or about A.D. 131, instructed the famous jurist Salvius Iulianus to revise and settle the praeto rian and aedilician edicts. The changes in substance do not appear to have been of a far-reaching character, but the edict as revised was henceforward made unalterable except by the emperor him , self.
The relationship between ius honorarium and ius civile has often been compared with that existing in England between common law and equity. In both cases we find, as Maine put it (Ancient Law, p. 25) a "body of rules existing by the side of the original civil law, founded on distinct principles, and claiming incidentally to supersede the civil law in virtue of a superior sanctity inherent in these principles," and in both cases the resulting duality enor mously complicates the law, but, of course, when we come to detail the comparison no longer holds.
Responsa Prudentium.—The force attributed to professional opinions of a certain type was another peculiar feature of the Roman system, and one which contributed in no small measure to its success, for it was the "learned lawyers" (prudentes) to whom the moulding of the law into a coherent system was really due.
Originally, according to an entirely credible tradition, law was considered the special province of the pontifices (see PONTIFEX), who seem to have regarded it as a mystery to be exploited in the interests of their order. Their monopoly was however broken down, according to legend, in 304 B.C., by Gn. Flavius, a clerk of Appius Claudius Caecus, who is said to have stolen from his master and made public, a list of legis actiones (i.e., forms of words which had to be followed exactly in the conduct of law suits), thereafter known as the ius Flavianum. The first known legal treatise, called the "cradle of the law" by Pomponius, is the Tripertita of Sextus Aelius Paetus Catus (consul 198 B.c.) which contained the text of the XII. Tables, the interpretatio put upon it by the jurists and the legis actiones. Probably the last part was
identical with the ius Aelianum which, according to Pomponius, was a collection of legis actiones like the earlier ius Flavianum.
It is plain in any case that from about 30o B.C. onwards there came into existence a class of men who made the study of the law their special interest. These iuris consulti or iuris prudentes were not professional lawyers in the modern sense, but men of rank who sought by giving free legal advice to obtain popularity and advancement in a public career. The responsa (answers) which they delivered to those who consulted them were of greater weight than are our modern "opinions of counsel" because the person who actually decided a case under the Roman system of procedure was not, as with us, a trained lawyer, but a lay iudex, who did not, like our Jurymen, have a judge to direct him on points of law. Augustus empowered certain jurists to give responsa with the emperor's authority, and this practice led, perhaps by insensible degrees, to the view that the iudex was bound to abide by the responsum of a jurist who had received this ius respondendi. Gaius at any rate mentions a rescript of Hadrian which laid down that responsa were binding if they agreed, and that if they disagreed, the iudex could decide for him self which to follow. (See Wlassak, Die klassische Prozessformel, P. 45.) The practice of conferring the ius respondendi appears to have fallen into disuse about the end of the third century A.D. when the classical period was over, but in the meanwhile, responsa had certainly come to be regarded as binding not only for the case for which they were originally given, but also as precedents for future cases, and, further, authority gradually came to be attached to the other writings of those jurists who had the emperor's pat ent. The "law of citations," an imperial enactment of 426, ulti mately laid down that only the works of five jurists, Papinian, Paul, Gaius, Ulpian and Modestinus, might be cited and, subject to some provisos which are obscure, the works of authors quoted by these five. If the authorities cited disagreed, the majority was to be followed ; if numbers were equal, the side on which Papinian stood was to prevail; if he was silent, the index might please himself.