What does it mean to be Catholic? Is it about loyalty to the pope? To bishops? To particular doctrines like Mary’s Immaculate Conception or Transubstantiation? While these things certainly are a part of Catholic faith, what this lecture will suggest is that being Catholic rests ultimately on something much more foundational. This is the principle of “sacramentality,” the conviction that what we know and experience in our everyday lives gives us a glimpse of what God is really like. It is because of the “sacramental principle” that we can speak of the seven sacraments being “outward signs” of God’s grace, that we can call statues and medals holy, that we can dare say that a hum an being can actually be the “Vicar of Christ,” and that all cultures are basically good. This is a vision, however, that needs always to be held in tension. Throughout history Catholics have both overstated or ignored the principle of sacramentality, therefore betraying it. And so Catholics need always to “reach for fidelity” to the Mystery that became a sacrament for us by becoming flesh and dwelling among us.