Christianity today is experienced as a multitude of faith communities with a common bond of belief in the Trinity and Jesus as Lord. Christianity began as a united faith, but the Great Schism that separated the Orthodox East from the Roman West broke this unity. The Protestant Reformation of the sixteenth century, however, was the event that splintered Christianity into the types of faiths we see today. The story of this fracture and the church's response are critical to the understanding of Roman Catholicism today.