Dipping into Greek East and Latin West. The Church AD 681-1071 as bedtime reading is probably not such a good idea, but does lead to interesting discoveries. I knew of course that one of the differences between East and West is their use in the Eucharist of leavened and unleavened bread respectively. I may even have heard that there have been controversies over it. But I did not know that it was the most explicitly invoked issue in the controversies of 1054. And, quite frankly, I don’t think that I would ever have been inclined to take it seriously as a cause of division. But the background that Father Louth provides is interesting.

It turns out that the Greeks interpreted the Latin use of unleavened bread against the background of their contacts with the Armenians, who also used unleavened bread. And given that the Armenians were so-called monophysites, their use of unleavened bread was interpreted against the background of their defective Christology

… in contrast to “the substance of our [human] dough,” which is “ensouled” and is what “the Word of God assumed and of which he became its hypostasis.” With this play on words, the argument is moving from being about the nature of the eucharistic bread to the nature of the Incarnation; the one mirrors the other, the leavened bread of the Eucharist mirroring the “ensouled nature” that, according to orthodox Christology, the Word assumed. Advocates of unleavened bread are both caught in the Old Testament, prior to the Incarnation, and betray a Christology in which the human nature that Christ assumes is defective… (312-313)

The Latins, by contrast, based their use of unleavened bread (which they probably introduced for practical reasons) on the supposed practice of Jesus in celebrating the Passover meal. They interpreted this against the background of Paul’s words in 1 Corinthians 5:6-8, which in Latin read “Do you not know that a little leaven corrupts the whole dough?”

Father Louth comments:

Two systems of symbolism, focused on the same liturgical act, developed, but they took their inspiration from the stark contradiction of leavened or unleavened bread. The refusal, on either side, to enter the symbolic world of the other could be presented as a fundamental apostasy. The Latins, with their unleavened bread, were Judaizing, or shrinking from acknowledging the full humanity of Christ (an objection that worked better against the Armenians); the Greeks, with their leavened bread, were virtual Marcionites, discarding the Old Covenant in celebrating the Passover with his disciples. (314)

This serves to underline the fundamental role that symbolic worlds play the challenge of entering into the symbolic world of the other.