The Latin Church confects the Eucharist in unleavened bread (azymes); the Christian East — Orthodox and Eastern Catholic alike — uses leavened bread. In 1054 this difference was sharpened into a weapon: Patriarch Cerularius charged that the Latins’ unleavened offering was no true Eucharist at all. It is worth answering plainly, because the bread itself was never a reason to divide.

The Latin reason is simple fidelity to what Christ did. The Synoptic Gospels place the Last Supper on “the first day of the Azymes” — the Passover, at which no leavened bread could lawfully remain in the house. So at the very institution of the Eucharist, the bread in Christ’s hands was unleavened; the Roman rite keeps to the bread that was on the table that night.

And the East’s leavened bread is no error — it is a beautiful theology. Leavened bread is risen, living bread; it signifies the risen Christ and the life of the Spirit quickening His Body. The East presses a sharp point too: in John’s chronology Christ dies as the Passover lambs are slain, so the Supper the night before need not have been the seder — and the word the Gospels and St. Paul actually use at the institution is artos, ordinary raised bread, never azymos. This is an ancient and venerable tradition, and the Latin Church has never called it invalid. Honesty adds that the Latin West itself used leavened bread for its first several centuries, adopting unleavened only in the early Middle Ages.

That is the heart of the matter: both are true. The Council of Florence defined that the Body of Christ is truly confected in “unleavened or leavened wheaten bread,” each priest following “the custom of his Church, whether that of the West or of the East.” The Eastern Catholic Churches use leavened bread today in full communion with Rome. The bread is a difference of rite, honored on both sides — not a difference of faith. The old charge that one was no true Mass was simply false.