Roman conservatism finds succinct expression in an edict of the censors from 92 BC, as preserved by the 2nd-century historian Suetonius: "All new that is done contrary to the usage and customs of our ancestors, seems not to be right." However, because the "mos maiorum" was a matter of custom, not written law, the complex norms that it embodied evolved over time. The ability to preserve a strongly-centralised sense of identity while it adapted to changing circumstances permitted the expansionism that took Rome from city-state to world power. The preservation of the "mos maiorum" depended on consensus and moderation among the ruling elite whose competition for power and status threatened it.