The dispute is not simply about adding a word, it is about what the addition claims. The original Greek creed said the Spirit proceeds from the Father, using a single verb, ekporeuomenon, that both traditions agree names the Spirit's ultimate origin. The Latin addition has the Spirit proceed from the Father and the Son as from one single principle, treating Father and Son together as one shared source. Photius, writing his Mystagogy of the Holy Spirit in the ninth century, argued this collapses the Father's unique role as sole origin of the other two persons and leaves the three persons of the Trinity poorly distinguished from one another, since two of them would now share the very same causal role. Rome and much of the West have preferred instead to say the Spirit proceeds from the Father through the Son, a formula many Eastern theologians accept as compatible with their own, since it keeps the Father alone as source while still giving the Son a real part in the Spirit's eternal procession. A 2003 agreed statement from the North American Orthodox Catholic Theological Consultation concluded the two formulas can be read as complementary rather than contradictory, provided filioque is understood in that through the Son sense and never as naming a second source standing beside the Father.