With Rome's collapse, the consensus mechanism in Europe fractured into two overlapping systems. Kings inherited power through bloodline. The Church ratified kings through coronation, and resolved doctrinal disputes through ecumenical councils of bishops. Between kings and kings, the feudal oath of fealty was the binding contract: personal, hierarchical, revocable only by death or excommunication. The first cracks in this system — Magna Carta, the Icelandic Althing, early parliaments — showed up as early as the 10th century but wouldn't compound into anything systemic for another 500 years.