That's a problem that plagues all of us. There are some theoretical things we can say about it, but I'd rather spend time on the practical.
The Roman Catholic Church believes that one function of the church is to be the authorized interpreter of Scripture. They believe that not only do we have an infallible Bible but we also have an infallible interpretation of the Bible. That somewhat ameliorates the problem, although it doesn't eliminate it altogether. You still have those of us who have to interpret the infallible interpretations of the Bible. Sooner or later it gets down to those of us who are not infallible to sort it out. We have this dilemma because there are hosts of differences in interpretations of what the popes say and of what the church councils say, just as there are hosts of different interpretations of what the Bible says.
Some people almost despair, saying that "if the theologians can't agree on this, how am I, a simple Christian, going to be able to understand who's telling me the truth?"
We find these same differences of opinion in medicine. One doctor says you need an operation, and the other doctor says you don't. How will I find out which doctor is telling me the truth? I'm betting my life on which doctor I trust at this point. It's troublesome to have experts differ on important matters, and these matters of biblical interpretation are far more important than whether or not I need my appendix out. What do you do when you have a case like that with variant opinions rendered by physicians? You go to a third physician. You try to investigate, try to look at their credentials to see who has the best training, who's the most reliable doctor; then you listen to the case that the doctor presents for his position and judge which you are persuaded is more cogent. I'd say the same thing goes with differences of biblical interpretations.
The first thing I want to know is, Who's giving the interpretation? Is he educated? I turn on the television and see all kinds of teaching going on from television preachers who, quite frankly, simply are not trained in technical theology or biblical studies. They don't have the academic qualifications. I know that people without academic qualifications can have a sound interpretation of the Bible, but they're not as likely to be as accurate as those who have spent years and years of careful research and disciplined training in order to deal with the difficult matters of biblical interpretation.
The Bible is an open book for everybody, and everybody has a fair shot of coming up with whatever they want to find in it. We've got to see the credentials of the teachers. Not only that, but we don't want to rely on just one person's opinion. That's why when it comes to a biblical interpretation, I often counsel people to check as many sound sources as they can and then not just contemporary sources, but the great minds, the recognized minds of Christian history. It's amazing to me the tremendous amount of agreement there is among Augustine, Aquinas, Anselm, Luther, Calvin, and Edwards—the recognized titans of church history. I always consult those because they're the best. If you want to know something, go to the pros.