From the 7 May 2005 mass in the Basilica of St John Lateran:
The Bishop of Rome sits upon the Chair to bear witness to Christ. Thus, the Chair is the symbol of the potestas docendi, the power to teach that is an essential part of the mandate of binding and loosing which the Lord conferred on Peter, and after him, on the Twelve. In the Church, Sacred Scripture, the understanding of which increases under the inspiration of the Holy Spirit, and the ministry of its authentic interpretation that was conferred upon the Apostles, are indissolubly bound. Whenever Sacred Scripture is separated from the living voice of the Church, it falls prey to disputes among experts.
Of course, all they have to tell us is important and invaluable; the work of scholars is a considerable help in understanding the living process in which the Scriptures developed, hence, also in grasping their historical richness.
Yet science alone cannot provide us with a definitive and binding interpretation; it is unable to offer us, in its interpretation, that certainty with which we can live and for which we can even die. A greater mandate is necessary for this, which cannot derive from human abilities alone. The voice of the living Church is essential for this, of the Church entrusted until the end of time to Peter and to the College of the Apostles.
This power of teaching frightens many people in and outside the Church. They wonder whether freedom of conscience is threatened or whether it is a presumption opposed to freedom of thought. It is not like this. The power that Christ conferred upon Peter and his Successors is, in an absolute sense, a mandate to serve. The power of teaching in the Church involves a commitment to the service of obedience to the faith. The Pope is not an absolute monarch whose thoughts and desires are law. On the contrary: the Pope's ministry is a guarantee of obedience to Christ and to his Word. He must not proclaim his own ideas, but rather constantly bind himself and the Church to obedience to God's Word, in the face of every attempt to adapt it or water it down, and every form of opportunism.
Pope John Paul II did this when, in front of all attempts, apparently benevolent to the human person, and in the face of erroneous interpretations of freedom, he unequivocally stressed the inviolability of the human being and of human life from the moment of conception until natural death. The freedom to kill is not true freedom, but a tyranny that reduces the human being to slavery.
The Pope knows that in his important decisions, he is bound to the great community of faith of all times, to the binding interpretations that have developed throughout the Church's pilgrimage. Thus, his power is not being above, but at the service of, the Word of God. It is incumbent upon him to ensure that this Word continues to be present in its greatness and to resound in its purity, so that it is not torn to pieces by continuous changes in usage.
The Chair is - let us say it again - a symbol of the power of teaching, which is a power of obedience and service, so that the Word of God- the truth! - may shine out among us and show us the way of life.
Read the whole thing here.