You are Peter, and upon this rock I will build my Church. We have to be careful in thinking about the image of the “rock.” The faith is not a rock, something solid and unchanging that I received from someone else and then hand on to others. The faith is alive and as such grows and changes, always in continuity to its “genetic structure.” The image Jesus left is that the Church is built on rock, on a solid foundation. But if you think about it if a house is built on a solid foundation it can develop over time. You add a extra wing when you need more space, you build a dormer to provide a new room. So a church built on rock.