Law is the primary Roman contribution to civilisation, especially the law of the Republic which was essentially private law. In its recovery (as it was developed under the Imperial partly-Christianised period) during the High Middle Ages, it became a significant factor in the emergence of the politically highly diversified but culturally highly unified Christendom. On the down side, Rome of the Imperial period was the ultimate source of the idea that sovereignty could be transferred from the people to their ruler.
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