Since I agree with you about the Trinity being thoroughly Biblical (save things like its name, as well other extra-Biblical words that we use to describe/define what we mean), I think that my understanding of "a doctrine that is created outside of the Bible" must be different than yours is. As far as there being any question about the fact that the doctrine of the Trinity is drawn out of the Bible, how could it be anything else (as no one is coming up with something like that on their own ).
I'll have to reconsider my "outside of the Bible" definition concerning doctrine (so for now I'll cast my vote the other way).
I'll have to reconsider my "outside of the Bible" definition concerning doctrine (so for now I'll cast my vote the other way).
For the sake of an example of a doctrine that is found from the outside the Holy Bible for instance you have heresies today such as Homosexual Marriage. This of course is not found in the Holy Bible, but rather originates from mankind. As it originates from mankind it naturally comes into direct conflict and contradiction of the Holy Bible on multiple levels; for example what the Bible says about that sin, what the Bible says about actual marriage, what the Bible says about the establishment of the churches, etc. Therefore it constitutes as being a heretical doctrine, and even if it is performed in a church that claims to be Christian, this does not make the heresy suddenly valid, but merely means that any church that holds this doctrine is excommunicated from the holy body of Christ.