The civil law tradition is the oldest legal tradition in the world today, embracing many legal systems currently in force in Continental Europe, Latin America and other parts of the world. Despite the considerable differences in the substantive laws of civil law countries, a fundamental unity exists between them. The most obvious element of unity is the fact that the civil law systems are all derived from the same sources and their legal institutions are classified in accordance with a commonly accepted scheme existing prior to their own development, which they adopted and adapted at some stage in their history. Roman law is both in point of time and range of influence the first catalyst in the evolution of the civil law tradition.