I am not a canon scholar, and this is just my personal opinion, but aren't these canons in place so that we (the Orthodox) do not put ourselves in danger of falling into heresy?
That's certainly an important reason, and one much more relevant in today's pluralistic society than at a time when Orthodoxy was the favoured religion of the Empire. However, I think it is also related to the concept of corporal prayer as the manifestation of the Church as the Body of Christ, united in a common faith.
I find nothing objectionable about the words of Surat al-Fatiha, for example, but I would not join in praying it with my Muslim friends who interpret those who "go astray" from the truth as referring to Christians. I'm not equating Muslims and Catholics, just trying to demonstrate how a difference in faith is not done away with just because we can find a set of words acceptable.
I could read the Creed, without the Filioque, with a Calvinist, yet we would not be meaning the same thing when we said "for our salvation." And if we do not mean the same thing, what would be the purpose of our common declaration?
I agree with you that there are times when prayer with Catholics is acceptable, and even right (your example of a dying friend being one such situation), but I think one should also consider whether prayer, like the sacraments, have their proper context in the Church of Christ and imply a common faith and life in Christ.
Well said, Orthodox11. I totally agree with you. I specifically confined my comments to Catholics because, I think when you go farther beyond (such as Calvinists and eventually Muslims), there are much larger problems at hand, and, honestly, I'm not sure how I would deal with those. Now of course, by the bed of a dying friend or loved one, their faith will not stand in the way of me praying, and praying with them. That, specifically, is a delicate situation which I would handle with care so as NOT to confess something contrary to our faith, but I would, indeed, pray for and with them.
In other cases, it is indeed more difficult and we must be careful and discerning. I'm not sure how I would handle other situations, to be honest, except to let the Holy Spirit guide me. In the example that you gave of saying the Creed with a Calvinist, of course our meaning is different. But my confession of the creed, my meaning, my faith, is not affected by what HE means. My meaning is clear, my meaning correct, and God knows that and knows the difference.
I will say that I think the purpose of the common declaration is not to achieve unity in prayer, but unity in cause, so to speak. Gathering together in an ecumenical service, we know, is NOT for the purpose of common faith, as our faiths are NOT common. The purpose is more unity in cause-- for instance coming together in prayer over abortion or a tragedy in the community (like 9/11). Ecumenical services do not unite us in faith, obviously. If only it were that easy. But they do unite us in "brotherhood" toward a common good, a common cause, and they advance the good feelings and Christian love that are necessary for open dialogue (that we might bring them to The Faith), for effecting change (such as in the case of abortion), and for ministering to the community (such as in the case of a tragedy like 9/11).
That's why it always irks me when people say we should not engage in ecumenism. IMHO, the purposes of ecumenism are those I've listed above, NOT uniting in a watered down faith. The latter being what those against ecumenism often think. This is a mistake, and not engaging in ecumenism is cutting off our nose to spite our face. We do not do away with our differences in faith, simply agree on what we DO have in common for the purposes of whatever that particular event aims at. It doesn't effect our confession of faith, we do not engage in heresy, but in compassion, mercy, and love, we recognize the importance of being present at such events, as we are THE Church and The Church SHOULD, no, MUST be heard on such issues. We don't condone the heresies of the other faiths, we exercise the virtues of mercy, compassion, and love, for the sake of the people, that they may hear the Truth.