The mos maiorum, literally translated as the “custom of the ancestors,” is the core concept of Roman traditionalism. As Ennius wrote:
- "Moribus antiquis res stat Romana virisque."
- (The Roman state stands on ancient customs and heroes.)
The mos maiorum was the unwritten code from which the ancient Romans derived their social norms. It is the core concept of Roman traditionalism, distinguished from but in dynamic complement to written law. The mos maiorum (plural mores, cf. English "mores") was collectively the "time-honored principles," behavioral models, and social practices that affected private, political, and military life in ancient Rome. Because positive law regulated few aspects of Roman daily life, traditional customs, by virtue of the auctoritas maiorum (“prestige or respect of the ancestors”), shaped most of Roman behavior.