The jurisprudence of Catholic canon law is the complex of legal theory, traditions, and interpretative principles of Catholic canon law. In the Latin Church, the jurisprudence of canon law was founded by Gratian in the 1140s with his Decretum. In the Eastern Catholic canon law of the Eastern Catholic Churches, Photios holds a place similar to that of Gratian for the West. Much of the legislative style was adapted from that of Roman Law especially the Justinianic Corpus Juris Civilis. As a result, Roman ecclesiastical courts tend to follow the Roman Law style of continental Europe with some variation. 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 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 Catholic Church developed the inquisitorial system in the Middle Ages. This judicial system features collegiate panels of judges and an investigative form of proceeding, in contradistinction to the adversarial system found in the common law of England and many of her former colonies, which utilises concepts such as juries and single judges. The institutions and practices of canon law paralleled the legal development of much of Europe, and consequently both modern civil law and common law (canon law having a significant effect upon the development of the system of equity in England) bear the influences of canon law. Edson Luiz Sampel, a Brazilian expert in canon law, says that canon law is contained in the genesis of various institutes of civil law, such as the law in continental Europe and Latin American countries. Sampel explains that canon law has significant influence in contemporary society. Sources of law The term source or fountain of canon law (fons juris canonici) may be taken in a twofold sense: a) as the formal cause of the existence of a law, and in this sense we speak of the fontes essendi (Latin: "sources of being") of canon law or lawgivers; b) as the material channel through which laws are handed down and made known, and in this sense the sources are styled fontes cognoscendi (Latin: "sources of knowing"), or depositaries, like sources of history. Fontes essendi The fontes essendi (Latin: "sources of being") include