Today is, I think, as well as being the Great Feast of Pentecost, the anniversary of the last occasion before 2013 upon which a Roman Pontiff abdicated. On June 4 1415, Pope Gregory XII, Angelo Correr, abdicated from the See of S Peter.
He did this for the good and the unity of the Universal Church Militant, which was gravely afflicted by schism. This had meant, for example, that if as a priest you walked outside the walls of the English town of Berwick to say Mass in a church within the adjacent Scottish county of Berwickshire, instead of saying una cum famulo tuo papa nostro Gregorio, you had to remember to say Una cum famulo tuo papa nostro Benedicto. Unless ... oops ... I'd forgotten this one ... you accepted the third pope, recently elected on the authority of a Council at Pisa and called John XXIII. Going into a strange Sacristy and looking around for the notice headed Nomen Papae must have afforded the travelling priest with endless surprises. Perhaps, after all, God is a God of Surprises.
Confusing times. Evidence of these confusions is still on public display in Westminster Cathedral, where a big and prominent List of Popes shamelessly displays a very uncertain attitude to the question of who was pope when and where and why in those diverting years at the beginning of the fourteen hundreds.
Disunity in Christ's Church Militant is always a bad and sad thing.