Greek Church has two principal nomocanonical collections, the "Nomocanon of John Scholasticus" of the sixth century and the "Nomocanon in 14 titles", which dates from the reign of the Byzantine Emperor Heraclius (), made by fusion of the Collectio tripartita (collection of Justinian's imperial law) and "Canonic syntagma" (ecclesiastical canons). The latter was long held in esteem and passed into the Russian Church, but it was by degrees supplanted by the "Nomocanon of Photios" in 883. Photius compiled systematically the canons of the East which amount to a counterpart of Gratian in the West. His 2-part collection, a chronological collection of synodal canons and his nomocanon revision with updated civil laws, became a classical source of ancient canon law for the Greek Church. Code of Canons of the Eastern Churches For Eastern Catholics, two sections of Eastern Catholic canon law had already, under Pope Pius XII, been put in the form of short canons. These parts were revised as part of the application of Pope John XXIII's decision to carry out a general revision of the Church's canon law; as a result, a distinct Code for members of the Eastern Catholic Churches came into effect for the first time on 1 October 1991 (Apostolic Constitution Sacri Canones of 18 October 1990). The Code of Canons of the Eastern Churches, as it is called, differs from the Latin 1983 Code of Canon Law in matters where Eastern and Latin traditions diverge, such as terminology, discipline concerning hierarchical offices, and administration of the sacraments. Jurisprudence of canon law The institutions and practices of canon law paralleled the legal development of much of Europe, and consequently both modern civil law and common law bear the influences of canon law. Much of the legislative style was adapted from that of Roman Law especially the Justinianic Corpus Iuris Civilis. After the 'fall' of the Roman Empire and up until the revival of Roman Law in the 11th century canon law served as the most important unifying force among the local systems in the Civil Law tradition. The Catholic Church developed the inquisitorial system in the Middle Ages. The canonists introduced into post-Roman Europe the concept of a higher law of ultimate justice, over and above the momentary law of the state. The primary canonical sources of law are the 1983 Code of Canon Law, the Code of Canons of the Eastern Churches, and Pastor Bonus.