In my work covering John Strickland’s books on Christendom, where he covers 2000 years of Christian history, both East and West, he has used the word Symphony to described the intended governance method of the East. The idea is that the emperor will rule as a proper Christian emperor, guided by the bishops.
Jonathan Pageau, in explaining the symbolism of the double-headed eagle, has offered his take on this governance model. He is asked, what is the symbolism of the double-headed eagle, especially as it relates to empire:
I have talked about this on the symbolism of the left and the right hand. It has something to do with authority and power; it has something to do with the two keys of St. Peter, of, let’s say, the Church and the state. You can understand it that way.
The Church as spiritual authority without physical power and the state as temporal power, physical power, whose authority isn’t in itself – it has to come from the other side. So, you can understand it as this mode of reality of spiritual authority and temporal power. At least that’s the way I understand that.
And those two are joined in Christ in a way in His icon. You actually see this manifested in the icon of Christ Himself, as the blessing hand: as Christ blesses, He manifests this direct authority. And usually in His left hand He has a book, this indirect or secondary aspect. So, you have direct language, then you have written language – which is like law or a materialized authority.
That’s the relationship between the spiritual and the temporal, and that’s the relationship between Church and state in the Byzantine understanding and later in the Holy Roman Empire in general. You see this symbol in the Austro-Hungarian Empire and the Russian Empire and all sorts of other places.
As I have noted elsewhere and often, the relationship of Church to emperor in the West was not the same as the relationship of Church to Emperor in the East. The former cannot be described as a state, while the latter more easily fits the description.
What I have read elsewhere: this symbol has been used in many places both east and west, Christian and Muslim – and Hittite before any of this. In Byzantium, it does appear to signify the Church and the state under one crown:
The two heads and two sceptres of the eagle symbolize the two authorities, the Church and the State under one Crown, the Christian Empire - one Empire under God. The co-existence of the Church and State in "Symphonia", a period of peaceful co-existence and co-operation, where the Emperor made into laws the decisions of the Church Synods (especially those of the Ecumenical Councils), while the Church authorities respected the laws of the State.
Another source explains it so:
The double-headed eagle is the most recognizable symbol of Orthodoxy today (other than the cross) and was the official state symbol of the late Byzantine Empire, symbolising the unity between the Byzantine Orthodox Church and State, which was governed by the principle of Symphonia or Synallelia, that is, a "symphony" between the civil and the ecclesiastical functions of Christian society.
This source continues to offer that the two heads also meant to cover east and west: Constantinople and Rome. Although, certainly by the time it appeared in the eleventh century in the east, this could only have been wishful thinking.
One author questions why it is so strongly associated with the Byzantine Empire at all, given its widespread use dating even thousands of years earlier.
Another author offers a similar interpretation as does Pageau – albeit, applicable to many cultures, not just Byzantine and not just Christian. The symbol represents physical power with one head, and spiritual power with the other. He states it may be used differently today, but historically it symbolized the representative of God on earth.
It is used in Scottish Rite Masonry, and is used on Russia’s coat of arm. What it meant or means elsewhere is secondary to this post. As Pageau offered toward the end of his statement, this is his understanding in the Byzantine context – which is also the context for the idea of Symphony raised by Strickland.
Sometimes a picture is worth a thousand words….