Complete the account of the formal structure of church authority before the schism.

Authority was distributed among five sees, known collectively as the pentarchy: Rome, Constantinople, Alexandria, Antioch and Jerusalem. Within it Rome held a primacy of honour rather than of jurisdiction, and the western claim that Peter’s authority passed to its bishops was argued most forcefully by Pope Leo I.

The gap between honour and jurisdiction is where the schism eventually opens. Constantinople could accept that Rome came first in a list; it could not accept that Rome could overrule a patriarch. Every later dispute — the filioque, the bread, clerical marriage — became load-bearing because this one was unresolved.