Many theories have been advanced for the cause of the fall of the Roman Empire. Gibbon, in his famous Decline and Fall of the Roman Empire, argued that Christianity was the essential cause of its collapse. Other theories include lead in drinking vessels, barbarian invasions, and the instability of a quasi-hereditary monarchy with ill-defined rules of succession.
More modern scholarship, though, takes a rather different perspective. Rather than accept the sixth century fall of the city of Rome to the barbarians as the end of the empire, scholars point out that what happened was actually a shift of power eastwards from Rome to Constantinople, caused by these weaknesses and barbarian invasions, and the Eastern Roman, or Byzantine, Empire flourished until the fall of Coinstantnople in 1453.