"That this purely Christian dogma actually for a second time rebelled against the Empire, and actually for a second time refounded the Church in spite of the Empire, is itself a proof that there was something positive and personal working in the world, other than whatever official faith the Empire chose to adopt. This power utterly destroyed the official faith that the Empire did adopt. It went on its own way as it is going on its own way still. There are any number of other examples in which is repeated precisely the same process we have reviewed in the case of the Manichean and the Arian. A few centuries afterwards, for instance, the Church had to maintain the same Trinity, which is simply the logical side of love, against another appearance of the isolated and simplified deity in the religion of Islam."
~G.K. Chesterton: The Everlasting Man, Part II, Chap. IV─The Witness of the Heretics.