This question deserves to be asked the hard way, with the Orthodox case put at full strength. The Orthodox Churches hold valid orders and valid sacraments — Rome herself says so. They claim to have guarded the faith of the seven ecumenical councils without adding to it, and they return a serious charge: that it was the West that innovated, adding the Filioque to the Creed and later defining as dogma what the first millennium never knew. Their liturgy is ancient and unbroken; their mystical tradition runs deep. A Catholic who cannot feel the force of all this has not understood the question.

So the Catholic answer is not “they lack valid sacraments” — they do not lack them. It is a question about unity: what, visibly, holds the Church together as one across the whole world and across the centuries, and gives her a way to settle a dispute when bishops divide? Christ Himself provided that, Catholics answer, in the office He gave to Peter — not as a rival to councils, but as their guarantor: the rock, the keys, the one charged to “confirm thy brethren” and to “feed my sheep.”

This is not merely a proof-text; it is a need that shows itself in practice. A council requires someone with authority to convene it, ratify it, and settle what it leaves contested. The Orthodox do not lack a principle of unity — they locate it in the conciliar consensus of the Church, received over time — but they have no final human tribunal to settle a dispute when that consensus fails, and the strain shows. The long-planned pan-Orthodox council of 2016 met, yet was boycotted by four of the autocephalous Churches; in 2018 Moscow broke communion with Constantinople over Ukraine, with no higher court to which either could appeal. In fairness, that 2018 rupture is a quarrel over jurisdiction, not the faith — Moscow and Constantinople confess the same creed, and neither calls the other heretical. And in fairness the other way: a final arbiter secures jurisdiction, not reception — Rome could define at Vatican I and Vatican II and still see the Old Catholics and the Society of St. Pius X break away. The papal office is no magic against division. What it offers is a visible court of last resort — a place where, in principle, a dispute is required to stop.

Two honest things, lest this become a cheap point. First, that argument from modern ruptures is an argument from effects, not from dogma — it illustrates the need for a visible center of unity; it does not by itself prove the papal dogmas, which must be defended on their own ground. And the Catholic Church has known her own grave failures of governance; the claim is structural, not a boast of good behavior. Second, the Orthodox “innovation” charge deserves a real answer, not a dodge — the work of the pages on the Filioque and on the development of doctrine. But when all of it is weighed, the question comes to this: did Christ leave His Church a visible principle of unity, or only the hope of one? Catholics believe He named that principle Peter — and that the Church is meant to be one, visibly, as He prayed she would be.