One of the things which has historically been a point of polemic and conflict between the Orthodox East and the Roman Catholic West is the use of the Filioque clause in the Creed. The word “filioque” is Latin for “from the Son”, and it is used in the classically western version of the Creed to describe the Person and procession of the Holy Spirit. In that version of the Creed, the Spirit is said to “proceed from the Father and the Son”.
Lesson from Church History 101: in the Councils of the Church in the fourth century (specifically the Councils of Nicea and Constantinople, held in 325 and 381 respectively), the divine natures of Christ and the Holy Spirit were emphatically set forth. Nicea declared the Son to be “light from light, true God from true God, of one essence (Greek homoousios) with the Father”. Constantinople declared the Spirit to be “the Lord, the Giver of life, who proceeds from the Father”. That is, the Spirit was not created by the Father as the angels were created, but rather proceeded from the Father's very being so that He was as divine as the Father was. These declarations of Nicea and Constantinople came together in the final version of the Creed, the one we recite today at Divine Liturgy. Much later, Christians in the far west (modern Spain to be precise) were hard at it, slugging away dogmatically and combatting the Arians there who still maintained that Christ was not homoousios with the Father. From the days of Augustine these western Christians believed that the Spirit proceeded from the Father and the Son. Everyone believed that, they felt (at least everyone in their western neighbourhood), so why not confess it in the Creed? That would stress in a big way the divinity of the Son and His equality with the Father. So when they recited the Creed, they sang that the Spirit proceeded from the Father and the Son. If asked they doubtless would have said that this was the original version of the Creed. And when they later met some Christians from the East who recited the Creed without the Filioque, they accused them indignantly of omitting this important clause. The reaction of those eastern Christians can be imagined. Since then, the East and the West have parted company, fighting over the use of the Filioque in the Creed (among other things).
It should be acknowledged that many thoughtful people in the world can make neither head nor tail out of this quarrel. It is, they feel, just one more example of the ridiculous and petty quarrelsome nature of the Christians, fighting tooth and nail over a single word. In particular, why are the Orthodox so stubborn over such trifles? At the end of the day, what does it matter? It's just a single word. Why can't the Orthodox East just chill out?
A few things may be said in response. First is the question of historical accuracy and honesty. Say, for example, that someone tinkered not with the Creed, but with the American national anthem. Say that someone said that the good ol' American anthem read, “Oh, say! can you see by the dawn's early light what so proudly we hailed at the twilight's last gleaming; whose dear maple leaf, through the perilous fight, o'er the ramparts we watched were so gallantly streaming?” Surely it would be only fair to protest and point out that the original version of the anthem did not extol the Maple Leaf, but the Stars and Stripes. One could change The Star Spangled Banner into The Maple Leaf Forever if one wanted to, but honesty should compel all involved to acknowledge that this was a change from the original. In the same way, surely it is reasonable for the Orthodox East to insist that if Christians say that they are reciting the Creed from the fourth century then that Creed should be recited in its original form, simply as a matter of historical honesty. Of course Orthodox go on to further insist that the Filioque addition is doctrinally erroneous, the venerable opinions of St. Augustine and other western teachers notwithstanding. But even apart from matters of historical honesty and doctrinal truth, there are other considerations which even secular people should be able to understand.
These considerations are two in number. First is the question of authority. When the western church after the Council of Trent (that was the anti-Reformation council of the sixteenth century, as you recall) wanted to appeal to authority, the first and strongest appeal was to the Pope in Rome. “Roma locuta est, causa finita est,” (i.e. “Rome has spoken, the case is closed”) was the basic mindset. That is, a Roman Catholic reflexively appealed to the central authority in Rome to determine the truth in matters of controversy. But the eastern church has always appealed not to a single living institution (i.e. the Papacy) but to the historical example of the Fathers. We Orthodox do not reflexively ask, “What does Rome (or New Rome) think?”, but rather, “What did the Fathers say?” For us, the first, strongest, and abiding authority is that of the patristic consensus. This is important, because it sets the tone for all our theology and for how we think and live today. For us, wisdom and the way forward into the future come from following in the trajectory of the past, not because we are bound by the limitations of those living ago, but because we are freed by them from the tyranny of the present, a present with its blind spots and its slavery to fad and fashion. For us, Tradition is not a strait-jacket, but a set of wings. It means that we do not have to keep on trying to re-invent the wheel, only to get the shape wrong because current fashion favours octagons over circles.
The second reason that the question of the inclusion or non-inclusion of the Filioque is important has to do with community. That is, to change the original wording of the Creed to include the Filioque would necessitate a new consensus of all the existing Orthodox churches. Take the example once again of the American national anthem. Recognizing that the original version spoke of Stars and Stripes, America could change it so that is spoke of the Maple Leaf instead of the Stars and Stripes, but this would require an impressive consensus of Americans, and would involve not talking about the “National Anthem”, but about the “Revised National Anthem”. (Even the Coca-cola Company had the decency to call New Coke “Coca-Cola II”.) In the same way, the Orthodox Church could decide that the Filioque was doctrinally correct after all and include the phrase, but it would have to speak not of “the Creed” any more, but of “the New Creed”, and this would require pretty much all the various autocephalous churches to sign on to it. What matters with us is community and consensus, and no major changes in things like the Creed can be made without without the whole community first agreeing to it. We march together as one. This means, given human timidity and the reluctance to move out of comfort zones, that change in Orthodoxy usually proceeds at a somewhat glacial pace. But given the catastrophic nature of changes which have occurred in churches outside her canonical borders, this may be a good thing.
The Orthodox reluctance to monkey with its Creed, that confession which has served as the doctrinal bedrock and the basis of unity, is entirely understandable. We think that the Creed as it stands to be historically original, doctrinally true, a witness to the patristic basis of our faith, and a safeguard of our conciliar unity. Not surprisingly therefore we will leave it as it is.