The Scripture readings for today's liturgy provide a biblical basis for the papacy, as John Bergsma explains. But as a Protestant, I was not able to see those verses as providing that basis, until I read Plato's Republic. Of the various philosophical factors that helped me become Catholic, one was teaching through Plato's Republic. I had taught it a few times before, but this time, I was teaching it with an eye toward its implications regarding unity. My conclusion was that for philosophical reasons we could expect Christ to have established for the Church an enduring office for her government, an office occupied by one person at a time. That conclusion allowed me to be more open and receptive to the Catholic understanding of Matthew 16:18-19, Luke 22:32, and John 21:15-17. So how did Plato's Republic help me reach that conclusion?
In order to explain the role of Plato's Republic in helping me become more open to the Catholic understanding of St. Peter's unique office in the Church, I need to lay out the broader line of reasoning to which it contributed. That line of reasoning was as follows.