Despite a long history of external threats and internal strife, the Roman Catholic Church and the broader reality of Catholicism remain a vast and valuable presence into the third millennium of world history. What are the origins of the Catholic Church? How has Catholicism changed and adapted to such vast and diverse cultural influences over the centuries? What great challenges does the Catholic Church now face in the twenty-first century, both within its own life and in its relation to others around the world? In this Very Short Introduction, Gerald O'Collins draws on the best current scholarship available to answer these questions and to present, in clear and accessible language, a fresh introduction to the largest and oldest institution in the world.