In antiquity, Roman law was a case-law system built up gradually through the creation and elaboration of specific remedies for particular fact-situations. The 6th century Byzantine emperor Justinian converted it into a collection of authoritative texts. They were rediscovered in the 12th century at Bologna and, since they provided arguments relevant to most problems of law and government, were studied in all European universities. Adapted by commentators, Roman law became a ius commune, which was ‘received’ to a greater or lesser degree into the national laws of modern European states.