The Filioque, or addition of the clause “and from the son” to the Nicene Creed, in the west brought the two halves of Christendom into conflict. Two issues were at stake- theology and authority. Was it theologically sound to state that the Holy Spirit proceeds from both the Father and the Son as the west came to believe? If so, by whose authority could the Nicene Creed be altered? http://joshhatala.wordpress.com/history/the-great-schism-of-1054-an-historiographic-view-by-josh-hatala/ Filioque Phrase
Researchers seem to disagree on what it was that the church eventually broke up over, but they all mention the ‘filioque’ phrase. This dispute centered on the fact that the west had inserted a special phase in the Nicene Constantinople creed, it indicated that the holy spirit proceeded from both the father and the son, rather than from the father through the son as the east believed. The east believed that only a council concerned with the unity of the whole Christian church could make changes like this to the creed. http://persuasive-essays.blogspot.com.au/2011/06/eastwest-schism.html The Filioque—Traditionally, the Nicene Creed spoke of the Holy Spirit "proceeding" from the Father only, but the Western Church began using the filioque clause—"and the Son"—an innovation rejected by the East and later declared by the Orthodox Church to be a heresy. https://www.newworldencyclopedia.org/entry/Great_Schism The insertion of the filioque clause into the Nicene Creed by the Roman church (western) in direct violation of the command of the Council of Ephesus, an action called non-canonical by the Eastern church. http://www.theopedia.com/Great_Schism Papal Authority
The primary causes of the Schism were disputes over papal authority -- the Roman Pope claimed he held authority over the four Eastern patriarchs, while the four eastern patriarchs claimed that the primacy of the Patriarch of Rome was only honorary, and thus he had authority