This is the procedural charge, not the theological one. Even a Catholic who is convinced the Spirit proceeds “from the Father and the Son” has to face it squarely: who gave the West the right to insert those words into a creed that the whole Church confesses in common? The Orthodox case here is strong, and pretending otherwise serves no one.

Their argument deserves its full weight. The Council of Ephesus in 431 forbade composing “a different faith” as a rival to the Creed of Nicaea, on pain of deposition. The Creed was promulgated by ecumenical councils — Nicaea in 325, Constantinople in 381 — so it is the common property of the universal Church, and no single patriarchate, least of all acting without a council, may amend what everyone confesses together. And the history embarrasses Rome: the Filioque was interpolated locally in Spain, spread through Charlemagne’s realm, and was pressed on Rome by the Franks — whereupon Pope Leo III, though he held the doctrine, refused to alter the text and had the Creed without Filioque engraved on silver shields in St. Peter’s to guard the original wording. Rome adopted the interpolated Creed only around 1014. Photius had already named the deeper worry: two sources in the Godhead seem to overthrow the Father’s unique monarchy.

The Catholic answer is not that the manner was tidy — it was not — but that Ephesus banned a rival faith, not a clarification of the same faith. The West read “and the Son” as unfolding what Nicaea already meant: procession through the Son, not a second, independent cause. St. Maximus the Confessor had defended exactly this in the seventh century, insisting the Romans “have not made the Son the cause of the Spirit.” And what one church could not do alone, a true ecumenical council could ratify: the Council of Florence in 1439, with the East present, declared the Filioque “lawfully and reasonably added to the Creed.”

But the concessions are real and should be made plainly. The original insertion was irregular — carried by imperial and Frankish pressure, not conciliar authority. Rome itself once guarded the unaltered text. And Florence’s union was repudiated in the East almost at once — formally rejected at Constantinople in 1484 — so the very mark of a true council the Orthodox demand, reception by the whole Church, is precisely what it lacked. That is why Rome today concedes what the silver shields once protected: the Creed of 381 without Filioque is normative, and its Greek recitation, in the words of the Vatican’s own 1995 clarification, “remains always legitimate.” The doctrine Catholics will defend on other ground; the manner of its addition they need not pretend was lawful in form.