I'm in the midst of an interesting conversation with someone, who, among other things, wonders if an "orthodox belief in the Trinity" is needed in order to be saved, or if requiring that belief is akin to adding to the Scripture. Here is my (slightly edited) response.
I'm not trying to add doctrines to the Scripture, or require more of salvation than what's required. At the same time, I do think we need to know and understand certain things about God in order to be saved. I don't think we need to have complete or perfect understanding, but I question whether or not someone who knows little about God can truly have a relationship with Him. I also question whether someone who understands what the Bible teaches about God, if they willfully reject some facet of Him, can truly be in a relationship with God. I don't see this as "adding to Scripture." Rather, I see it as a necessary consequence of knowing God in the first place. Without knowledge of Him, how can we have a relationship with Him? (cf. Acts 17--the unknown god).
I should also add that this is not just a theoretical exercise; it's very practical to me. I have children, and I wrestle with how much they need to know & understand in order to be saved. I don't think they need perfect or complete understanding in order to be saved. But if they have knowledge of God and reject it, does it make sense to believe they are saved?
Again, I'm not trying to add lines where none exist. What I'm trying to say is, if there is a fundamental doctrine about the nature of God that someone rejects, can they still be rightly called a follower of God? My answer to that question (at this point, anyway) is no. I believe the Trinity is one of those doctrines, hence my questioning whether someone in that state is a believer. It's not about the Trinity, per se.
Finally, let me say that I think there is a difference between cautious questioning and open rejection. I don't think we should merely parrot others' beliefs about something. That said, if someone honestly rejects the God of the Scripture in any aspect, on what basis can they claim to have a relationship with Him?
The new Shepherd's Fellowship blog has a post by John MacArthur which has something to say about this issue of belief.