Content of the Corpus Juris Civilis
Leaving aside the later legislation of Justinian and his successors, three works constitute the definitive restatement of Roman law that Justinian promulgated.
For the study of Roman property law the least important of the three is the “Code” (Codex), a collection of approximately 5,000 imperial “constitutions”—meaning the product of an emperor's legislative, judicial, or administrative enactments— from the reign of Hadrian (114-138 ce) to the date of the Code's promulgation (initially 529 ce, subsequently updated and reissued in 534 ce in the form that now survives).The second Justinianic compilation, which is far more important for an understanding of Roman juristic reasoning and doctrine covering the entire range of Roman private law, is the Digesta or “Digest,” a collection of excerpts from the most important and influential juristic literature of the Roman legal tradition. The task of compiling the Digest was formally begun in December of 530 ce, and the finished compilation was promulgated as positive law by Justinian exactly three years later (December 16, 533). As the act of promulgation states, “nearly 2000 books and more than 3 million lines” of juristic writing were reviewed and excerpted by the compilers for incorporation into a work of 50 books containing 150,000 lines of text. That work is the Digest. Since the source of every excerpt in the Digest is explicitly cited, we know that the excerpts are drawn from a total of 39 authors and 203 different works that range in size from a single “book” (manuscript scroll) to treatises of 80 and more “books.” The great preponderance of the 39 authors lived and wrote in the first two and one half centuries of the common Era, a period that modern scholars accordingly call the “classical period” of Roman jurisprudence. The Digest is therefore our chief witness to Roman legal science in its most productive era.
The “post-classical” jurisprudence that has survived is, generally speaking, more prone to dogmatism and reliance on established authority rather than independent legal reasoning. Of the pre-classical jurists, called the “elders” (veteres) in later texts, undoubtedly the most important was Q. Mucius Scaevola “Pontifex” (d. 82 bce), whose 18 books of Commentary on the Civil Law might fairly be considered to have marked the beginning of Roman juristic literature.A third Justinianic compilation was published at the same time as the Digest and has been equally influential. This is the Institutiones (“Institutes”) of Justinian, a textbook that was intended to serve as the authoritative introduction to and synopsis of the totality of Roman law. The four books of the Institutes follow an arrangement and program that was apparently created by the jurist Gaius nearly three centuries before. They present Roman law as a logically coherent and comprehensive system of doctrines. Justinian’s framework has been immensely influential on how law, as an object of study and body of doctrine, came to be thought of in both civil and common law jurisdictions.[7] One can still detect its vestiges in the structure of modern civil codes in the Roman tradition.