The author proves that the mos maiorum has a political value and highlights the evolution and crisis of this concept during the late Roman Republic. The mos maiorum is the ruling class’s foundation of power. The dominant political faction invokes the mos maiorum in order to legitimize its political authority. This faction is originally comprised of the patricii, who are later replaced by the patrician-plebeian nobilitas, in the half of the 4th century B. C. Finally, the power of an elite category of citizens, known as optimates, evoke the mos maiorum in order to legitimize their political power. The optimates embody the values of the ancestors. In the Late Roman Republic the mos maiorum is in great crisis. The moral degeneration linked to the crisis of the mos maiorum causes the political downfall of the res publica. The ruling class is principally responsible for the crisis of res publica; its absence of political unity is the essential reason for the downfall of the res publica. The evocation of the mos maiorum made by Cicero fails, because the res publica is not that of the time of the maiores, but it’s only a dim of the Rome of the ancestors.
