The Filioque controversy is an immensely puzzling theological dispute. For instance, the Catholic Church condemns the use of the Greek expression και του Υιου in Greek formulations of the Nicene Creed. It uses Filioque, however, in Latin formulations. This fits very well with the Catholic position that arose out of the combination of II Lyons and Florence. In essence, the position is this: the Greek Symbol, without the και του Υιου, is most accurately translated into Latin using the Filioque, due in part to complications in translating the Greek το εκ του Πατρος εκπορευομενον into Latin. So, in conformity with the Latin Fathers, they translate it as qui ex Patre Filioque procedit. Thus we have the odd situation that, from the Latin point of view there is no real controversy; they affirm the Greek position, and just hold that they had to translate the Greek into Latin using the Filioque because without it the Latin implies subordinationism. Translate into Latin from the Greek, you have to use the Filioque, because otherwise the Latin loses something suggested by the Greek; translate from the Latin into Greek and you do not add και του Υιου, because that implies something false that the Latin does not. The Greek position, from this perspective, ends up being simply that the Latins don't know what the Latin means. Thus, as far as the Catholics are concerned, the Orthodox are perfectly orthodox Catholics in denying the και του Υιου. Hence, the Catholic position on the Orthodox is that there is nothing in this to prevent communion; the two sides are (on this point) in complete doctrinal agreement. And, naturally, Protestants who affirm the Filioque have similar views. From the other perspective, the view is very different. And so we have a theological dispute in which the dispute has become whether there is actually a dispute; one side says it's all just verbal, and the other side says it's crucially substantive.
I was reminded of all this by Jeremy's excellent post on preservation of form and meaning through translation in the case of the Bible.