(Part one of three)  The Nicene Creed did not originally have the Filoque. Its addition led to the Great Schism. The similarity with the Reformation lies in both events involving a betrayal of Scripture perceived by the dissenting parties-the Orthodox Church and Martin Luther.—Robert Helfman  

Until just now, I had not taken the addition of the Filioque to the Creed seriously.  The Church added the Filioque fifty-six years after Nicaea I (325) at Constantinople I (381).  I have not considered that important for the 1054 break between east and west, though others may.  On the other hand, the first official proclamation of a creed with the addition of the Filioque came in 589 with the Third Council of Toledo.