Ever misplace your keys? Not fun. It throws the whole day into confusion and panic until they're found. Keys unlock barriers that prevent access to what we need for normal everyday functioning, such as home, auto, office, etc. Until we get them back, we are locked out, unable to gain entry to those places or things around which life is ordered. Consequently, the absence of the keys creates dis-order.
In addition to access, keys can also represent authority. We see this most clearly at play in office dynamics. I might have a key to the building and to my own office area, but other areas of the workplace may be opened only by a select few to whom the appropriate key has been entrusted. The ones who have those special keys, particularly the all-important master key(!), are those who typically have the greatest authority. (Perhaps I should be speaking today in terms of key fobs, swipe cards, access codes and the like, but the idea is the same.)
In the Gospel we heard on Sunday (cf. Matthew 16: 13-20), both access and authority unite in the symbol of the keys entrusted by Jesus Christ to St. Peter: "I will give you the keys of the kingdom of heaven, and whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven." These words are the foundation for the unique role of Peter and his successors, the popes, in the life of the Church. They are the reason statues of St. Peter usually portray him bearing keys, and why the coats of arms of the popes include an image of keys. They represent access (the grace of forgiveness communicated through the sacraments) and authority (teaching and governance in the name of Christ). These keys cannot be misplaced, because we know they have been uniquely entrusted to Peter, to the apostles in communion with him (cf. also Matthew 18:18) and to their successors.
It is quite extraordinary, to say the least, to see a mission of such importance as this entrusted to an individual whose weakness and mistakes were on constant display, and to his successors, who also know (like all of us!) the reality of human limit. When Pope Francis was asked in an interview to describe himself, the first thing he said was "I am a sinner." Herein, though, we are given another "key" that gives order to the entirety of our Christian lives: faith. Faith is the recognition of the truth of Christ, and the consequent realization of our total dependence upon his mercy. By the gift of faith, Peter was able to recognize the truth that Jesus is "the Christ, the Son of the living God." From this profession of faith, Jesus established Peter as the rock upon which his Church would be built. This establishment was not a removal of Peter's weakness but a pledge to work through it. This is why we can submit with serenity and confidence to the teaching of those who succeed to Peter's place and the direction they give to the Church. It is also a reminder to each of us to make daily our profession of faith, to acknowledge our weakness, and to rely peacefully on the loving presence of Christ acting in our own lives.