Jus commune or ius commune is Latin for "common law" in certain jurisdictions. It is often used by civil law jurists to refer to those aspects of the civil law system's invariant legal principles, sometimes called "the law of the land" in English law. While the ius commune was a secure point of reference in continental European legal systems, in England it was not a point of reference at all. (Ius commune is distinct from the term "common law" meaning the Anglo-American family of law as opposed to the civil law family.) The phrase "the common law of the civil law systems" means those underlying laws that create a distinct legal system and are common to all its elements. The ius commune, in its historical meaning, is commonly thought of as a combination of canon law and Roman law which formed the basis of a common system of legal thought in Western Europe from the rediscovery and reception of Justinian's Digest in the 12th and 13th centuries. In addition to this definition, the term also possibly had a narrower meaning depending upon the context in which it was used. Some scholars believe that the term, when used in the context of the ecclesiastical courts of England in the fourteenth and fifteenth century, also "meant the law that is common to the universal church, as opposed to the constitutions or special customs or privileges of any provincial church." The ius commune had a double basis: the Ancient Roman laws, as collected in Justinian's Corpus Juris Civilis, and the canon law of the Catholic Church, as initially collected in the 12th century in the Decretum Gratiani. While Justinian's collection remained unchanged throughout the medieval epoch, the canon law continued to be expanded and revised by various popes, reaching its final form, the Corpus Juris Canonici, in the 16th century. That "there were two highest laws, the canon and the civil" (Roman) law, remained a source of tension throughout the period in which the ius commune was influential. While Justinian's laws themselves did not change, their understanding and interpretation developed throughout this period.