Learning to do Theological Triage

It's an idea that's hardly original (I first heard of it from Al Mohler, but who knows who was the first to make the argument), but of great necessity today in Evangelicalism. It is the difference between hurt feelings and doctrinal purity; time-consuming endless debates and decisive breaks of fellowship. This idea is called theological triage. Most are familiar with these two words, but perhaps not when used together; theology being the study of God, particularly in a Christian context as revealed to us in the Scriptures; triage being the medical practice whereby doctors treat the most dire and urgent needs first before treat the lesser injuries (i.e. treating a gun-shot victim before treating a severe splinter). This practice allows doctors to save lives in the most efficient manner.
Theological triage, then, could be described as treating various aspects of the Christian faith according to the fundamental nature to the faith. In other words, there are primary issues, secondary, and tertiary (and if you really are up to it, I imagine you could keep going from there.) Primary issues are those things that without which, the Christian faith is no longer the Christian faith. These are the doctrines that make us Christian such as Justification by Faith, the Virgin Birth, the Trinity. If a church or group of people reject a primary issue then we can no longer have Christian fellowship.
Secondary issues are those issues which do not determine one's orthodoxy, but does affect how much cooperation we can have with one another. These issues include, but are not limited to, infant baptism, church polity, etc. While we may be able to work with, worship with, and fellowship with those who have different views on secondary issues, we cannot plant a church with them. For example, two of my closest friends are an Anglican and a Presbyterian. I love them to death, but the baptism thing would prevent us from planting a church together.
Tertiary, and subsequent levels you may want to devise, are those issues which are a matter of personal practice. Depending on the culture and prevalent views, most often you can do all the above and more with those whom you simply disagree with on such issues. These issues may include the use of tobacco and alcohol, styles of preferred worship and dress, etc. We can easily worship and serve in churches together with those whom we disagree on tertiary issues.
It is vital that we as Evangelicals, both locally and globally, learn to distinguish primary from tertiary issues. Many a useless battle has been waged over tertiary issues needlessly. Many believers, in fact, change their views on tertiary issues throughout their life, and so we should not be so quick as to draw a line in the sand over such topics. Further, we must remember that it is our Faith which we must defend and protect, not necessarily the ways we practice it. I can remember massive church debates in the mid-90s over "contemporary" music, folks willing to quit the church if the church allowed a guitar to be played. (F.Y.I. when it first came out the pipe organ was view in the same light, seen as an abomination to God's worship.) It was a useless and self-centered war over the tempo and accompaniment of God's worship. Few were concerned with the actual worship of God, they were more concerned about the mode. And while God's worship is something we should take seriously, we mustn't lose the real meaning over differences of personal tastes.
The same rings true today of any tertiary issue. They are important to discuss and to edify one another with, but we must not lose the Gospel in our obsession with lesser issues. Our personal convictions are good, but we must not mistake my own interpretation as infallible and the law of God. Where Scripture allows leeway, let us do the same, so long as we remain fully committed and devoted to the advancement of the Gospel for the glory of our great God.