How do we distinguish between primary & secondary issues from the Bible?

There is a fascinating thread going on right now over at Phil Johnson's blog regarding, in his words, "the biblical basis for making a distinction between primary and secondary issues." This is fascinating for a couple of reasons. First, because he says he's read very little if anything about it. Although he reads lots, Phil probably isn't the guy who's read the most theological stuff (I'm guessing that honor would go to Al Mohler), but as he admits that this is an area that's of interest to him, I'm sure he's constantly on the lookout for this kind of material, and with all of the resources at his disposal--with all of his knowledge of Church History--he's still come up mostly empty. That's saying something.

The other reason this is so interesting (and important) is the implications it has for all who claim Scripture as our only authority. If we don't know the difference between primary and secondary issues, how do we know when to admonish and when to encourage? How do we know when to focus on unity and when to focus on truth? Are men who suggest breaking fellowship with those involved with ECT overreacting, or are they being Biblical? What is my Biblical basis for making this decision? There are many decisions like this that need to be made, and too often the basis for making these decisions is anything but Scripture.

Interesting issues. I trust Phil will continue working his way through this. After all, it isn't a spur-of-the-moment issue--I just listened to an MP3 from March where he addressed it. I would assume the Shepherd's Conference, but I got it from his GraceLife link. The message title is "Dead Right--the Failure of Fundamentalism" (don't let the title put you off--it is good stuff).