And since Newman, the doctrine of the development of doctrine has developed. ;-}

Tridentinus, we both know full well, perhaps more than some on this forum, this is the fundamental issue that divides conservative and progressives at depth. I suspect I may soon have to withdraw from NCR for while, so I dare not get into a serious discussion with you on this core issue just now. 

Somewhat light heartedly, then, may I suggest if we could place ourselves intellectually back at the end of the 3rd century, prior to the christological and trinitarian councils, and have only scripture as our guide, a hundred competent Christian intellectuals are NOT likely to have come to the same conclusions as those great councils. Numerous views would emerge in our study  of scripture and many would have been heretical by today's standards.

I suggest the guidance of the Spirit was required to lead us beyond the tradition as then perceived to something genuinely new and marvellous, literally beyond words.