The term mystery, applied to the Church, signifies many things. It implies that the Church is not fully intelligible to the finite mind of man, and that the reason for this lack of intelligibility is not the poverty but the richness of the Church.
In the end, perhaps, one has to accept a reverent silence about the Church -- or about any theological reality.
In Models of the Church, one of America's leading theologians defines the basic functions of the Church, assesses its mission on Earth, and explores its many different roles in the lives of believers.