The Church has survived itself
The claim
Across two millennia, the Catholic Church has been led by saints and by criminals, has prevailed against the Roman empire, Arian heresy, the fall of Rome, the Reformation, the French Revolution, Marxism, and modernity, and is still teaching the same Creed.
On purely sociological terms, this should not have happened. Institutions led that badly do not survive that long. The persistence of the Church through her own corruption is a stronger argument than her flourishing under saints would have been. What needs explaining is not that Christianity has good periods — every movement does — but that this particular institution, with this particular structure and creed, has persisted at this scale through repeated catastrophic failures of its own leadership.
She has died often, and risen often.
I count many times the Church has been declared dead — by Diocletian, by Julian, by the Goths, by the Iconoclasts, by Voltaire, by Napoleon, by the architects of the cult of Reason, by Bismarck, by Stalin. After each, she has risen, often in places her opponents had not thought to watch.
An institution that can survive its own emperors, its own popes, its own scandals, and its own intellectuals, and continue to draw new converts on every continent, is not an ordinary institution.
Compare this to the Protestant fragmentation that began in the sixteenth century. What started as a reform movement has produced, by the most cautious counts, tens of thousands of denominations within five hundred years — an order of magnitude more division in a quarter of the time. This is not a sneer; it is a structural observation. Visible institutional unity, sustained through centuries under strain, is precisely what Christ promised when he said the gates of hell would not prevail. The contrast is what makes the Catholic case visible.
She is held by something other than her merits.