 The evolution that Kantorowicz described is formative, for sovereignty is a signature feature of modern politics. Some scholars have doubted whether a stable, essential notion of sovereignty exists. But there is in fact a definition that captures what sovereignty came to mean in early modern Europe and of which most subsequent definitions are a variant: supreme authority within a territory. This is the quality that early modern states possessed, but which popes, emperors, kings, bishops, and most nobles and vassals during the Middle Ages lacked.