It may seem rather odd, the idea of celebrating the feast of someone’s chair. I suppose, in fact, it is actually very odd. However, in the context of whose chair we celebrate, namely St Peter, we should take note of a deeper significance than a superficial celebration of a piece of furniture.
The seat or ‘cathedra’ of a bishop is, traditionally, the place from which the bishop preaches. It is a sign of his authority. Pope Benedict spoke of the ‘cathedra’ as ’literally meaning the established seat of the Bishop, placed in the mother church of a diocese which for this reason is known as a "cathedral"; it is the symbol of the Bishop's authority and in particular, of his "magisterium", that is, the evangelical teaching which, as a successor of the Apostles, he is called to safeguard and to transmit to the Christian Community’.
St Peter, of course, held a preeminence among the other Apostles, and as Catholics we believe St Peter was charged with particular care for the entire flock of Christ. Whereas ordinary bishops have particular care for those who fall under their local jurisdiction, the Pope, as successor of St Peter, has a special care for the entirety of the flock worldwide. I also like to think that this means each bishop too has someone therefore to care for them!
Today we celebrate and give thanks to God for the graces and authority given to Peter by Christ, and for the continuing role of the Petrine ministry as being a point of unity for the universal Church. We should pray especially for the Pope that he may be a faithful disciple of the Gospel and that he may govern and guide the Church in the way of truth, steering her through the tumultuous storms of time as she journeys on to her final destination.