Which Catholic doctrines stand only on interpretation?
I think you misunderstood my question.
You said "If all the councils used the Scripture as the final authority on doctrine, and the Pope had follwed them, we wouldn't be out of communion. "
I asked my question regarding this hypothetical situation - one where everything you said happened to be true - which in history, isn't how it worked out because in numerous Councils, because the parties involved couldn't agree on what Scripture was saying. In numerous cases an outside arbiter and extra-Scriptural language was necessary. Nicaea is a good example of such a situation.
And so I will re-ask my question, now that I have explained it: In a situation where everyone agrees to use Scripture as the final authority on doctrine, who becomes the arbiter to settle disputes of interpretation, and what method do they use to make such a judgment?