A cautious comment must here be inserted about the word ‘Church’. To the Christians of the East the Greek word ecclesia, or ‘church’, has always meant the whole body of the faithful, alive and dead. This is the Church mentioned in the Creed. But in practice, especially in the West, we use the ‘Church’ more and more to describe the priestly hierarchy, as opposed to the lay authorities. Indeed, owing to the deficiency of the English language, there is no other suitable word for the hierarchy. But in contrasting Church with State we are making a distinction which would have been meaningless to the Byzantines; and in making it we are committing a historical and philological error.
My two cents
The semantics of words like church have important implications—the above quote explains why. I like how the Byzantine worldview saw the church’s reach in a much broader, less institutional fashion than people do today (I wonder how many anti-Christians understand this point). If that’s the conception that existed in days gone by, it’s a tad annoying that we haven’t stuck to it.
It reminds me of debates between Christians and atheists, where if the Christian has the atheist on the ropes when referring to God, the atheist will sometimes backpedal and ask rhetorically, “which God?” (as if it solves the debate). If that’s how it’s going to be, then two can play at that game. If atheists call for separation of church and state, then I’m going to say, “which church and which state?”
If they answer “all of them”, they’ve made the same philological error mentioned by Runciman; using the Byzantine conception (which precedes the current-day conception), there is only one church i.e. the whole body of the faithful, alive and dead.
Runciman, S. (2003). The Byzantine Theocracy. Cambridge, Cambridge University Press, p. 4