The most important was the inclusion of the "Filioque" or "and the Son" in the universal Niceno-Constantinopolitan Creed. This was the beginning of the struggle between papal and conciliar power in the Church.

The Western view that the Spirit proceeds eternally from the Son, as He does from the Father, was also a major problem. St Photios the Great and Equal to the Apostles, Patriarch of Constantinople, opposed the Filioque and the theology behind it in his "Mystagogy of the Holy Spirit."

Growing papal jurisdictional claims over the entire Church, in addition to the universally accepted Primacy of Honour, was another important issue.

There were also local jurisdictional issues that added to the tension and conflicts between East and West, for example, the issue of which Church Bulgaria was to be under. Such conflicts were also highlighted in the time of Sts Cyril and Methodius, Apostles to the Slavs, in their struggle with the Roman Catholic Church in Germany.

A number of local liturgical usages in the West that broke with what Ecumenical Councils had established as universal norms also heightened tensions.

For example, the Roman popes cancelled Wednesday as a day of fasting and established Saturday as such. Such a ruling was clearly a flexing of papal jurisdictional muscle over and above the authority of the Councils that established Wednesday, the (fourth) day on which Judas went to betray Christ and so the beginning of Christ's Passion, as the day of fasting. Saturday was previously unknown as a day of fasting, save for Holy Saturday alone.

So it was less an issue of what may seem as an "insignificant" fasting rule and more of an issue of popes feeling they could unilaterally overrule Ecumenical Councils. Conciliar versus papal authority was to haunt the West as an ecclesial issue even after the break between East and West, most notably at the Council of Constance that saw the burning of Jan Hus in 1415 and later with the igniting of the flames of the Reformation.

Such were other Latin usages condemned by the Orthodox East such as the use of "azymes" in Holy Communion.

This reflected a break in the West between "symbol" and "what the symbol re-presented." Since the Communion Bread represented the Risen Christ, it needed to symbolize this through being bread that had "risen" or was leavened.

The entire argument over the nature of the symbolic was to revisit the West again on the eve of the Reformation when the Protestants who claimed that Rome had suppressed the "symbolic" in the Eucharist then compounded the issue by claiming that if the Eucharist was a "symbol" then it could not be the "Real Presence" of Christ. Orthodoxy has always maintained the Eucharist is BOTH.

The Eastern list of the "Errors of the Latins" grew with successive centuries, and included the condemnation of the Latin practice of making the Sign of the Cross on the floor with the finger, and then kissing it. This, once again, contravened a conciliar directive that forbade placing Crosses on the ground where people could walk over them . . .

Ultimately, however, the definitive break between East and West occurred with the Sack of Constantinople.