If you have been part of the missional conversation for any length of time then you've no doubt you've seen Christendom - that ancient notion of a Christian nation - being fairly heavily critiqued. But, have you ever spotted the elephant in the room? The fact that the first Christian empiror, the author of Christendom, was also the sponsor of the Council of Nicea, where that premier document of orthodoxy, the Nicean Creed, was first crafted. So,
Can we deconstruct Christendom without deconstructing orthodoxy?
Do we risk heresy by challenging Constantine?
Having given this some consideration, I say no. For to make such a suggestion is to imply that everything which came before Constantine was heretical, which would make Constantine our Messiah, not Christ. Moreover, church leaders were distinguishing between authentic and inauthentic Christianity way before Constantine, even within the New Testament itself. Nicea did not create orthodoxy, it merely clarified it, as clarifications became more necessary.
To get down to brass tacks, the teaching of the Trinity did not emerge out of nowhere at Nicea. More than a century before, Tertullian was using the words "Trinity", "person" and "substance" to explain that the Father, Son and Spirit were "one in essence – not one in person". In fact, the word Trinity was being used as early at 170 AD, by Theophilus of Antioch.
And of course, their teaching was itself rooted in the baptismal formula of Matthew 28:19 and the blessing of 2 Corinthians 13:14 and other teachings from the New Testament. It was not a burst of imagination and invention, it was the end product of a long process of clarification and contextualization. Imagination was the strength of the gnostics; memory was the strength of the traditionalists; and Nicea drew on memory.
So, the essense of my position is this, if it is possible to speak of Christian orthodoxy prior to Christendom, if it is possible to speak of Christian orthodoxy post-Christendom.