If salvation depends on a perfect knowledge and understanding of God and His will, then we are all screwed. But I think that a gracious and infinite (and infinitely gracious) God grants a lot of leeway to his finite creation for their lack of understanding.
For instance, the Church of Christ denomination thinks that it’s God’s will not to use musical instruments in worship services. In my church, though, we use lots of musical instruments because we don’t think God cares one way or the other. One of us is right, or at least righter than the other one. But even if my church is wrong about this, I don’t expect to be kept out of heaven because of it. If I show up at the pearly gates along with Church of Christ Guy, I don’t expect God to say to him, “Welcome home, obedient Church of Christ Guy!” and then say to me, “Hope you enjoy tickling the ivories in the fiery furnace, Liberace.”
I’m sure there are lots of examples like that — theological details that allow for different opinions, but your opinion about them doesn’t really have an impact on the condition of your immortal soul.
However, there must be a point at which your beliefs are so wrong that you cease to be a believer. Or at least you cease to be a believer in the God of the Bible, and you start to become a believer in something else entirely.
Contemporary theologian Katy Perry recently mentioned that she believes in God, but that she also has “a lot of spiritual, New Agey stuff that I’ve applied to my life now.” My question, when I hear something like this, is, How much New Agey stuff can you put in your life without pushing out things that have to do with a very Old Agey God? If you feel like you have to add anything, do you really believe in a perfect, complete God, or do you believe in some caricature of God? And is believing in a caricature enough to make you a Christian?
Bear in mind that I’m not talking about “cafeteria Christians” — those who pick and choose the parts of the Bible they’re going to believe and ignore the rest because they find it inconvenient or distasteful. I’m talking about people who deeply and sincerely believe things that are not true. Can you genuinely think you are pursuing God, but be wrong enough about it that you fall outside of His grace?
I don’t have any answers; just throwing it out there. I think that our best bet is to count on God’s grace, but that’s true whether we’re right about theology or not.