You reason in steps, and the steps are public. Grant that God exists and that Jesus is God, who rose from the dead. He then did something specific: He founded a single, visible Church on Peter — “thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it” (Matthew 16:18). That promise has a consequence: the Church He founded still exists somewhere today, unbroken. The only real question is which one.

Identify it the way you identify anything across time — by continuity. The Church Christ founded would be one (united in faith and government), holy, catholic (universal, for all nations), and apostolic: traceable by an unbroken line of bishops back to the Apostles. Run the test through history and the field narrows fast. Only the Catholic Church holds all four at once — a single worldwide communion, governed by the successors of the Apostles in union with the successor of Peter, teaching the same faith across two thousand years. Even the name is ancient: around the year 107, St. Ignatius of Antioch already wrote of “the Catholic Church.”1

This is not a claim that everyone else has nothing. The Eastern Orthodox preserve real apostolic succession and valid sacraments — which is exactly why their separation is a tragedy and not a mere difference of opinion.2 But succession alone is not the whole test; it must be succession in communion with Peter’s chair, the visible principle of unity Christ Himself named. The continuity argument walks this through case by case — including the hard ones, like 1054 and the Reformation.