Is adherence to Lutheran doctrine necessary for salvation? If so, by whose authority? Luther's (or his successors')? And if Lutheran doctrine is not necessary for salvation, what is its purpose? I do not mean to sound inflammatory, but I am curious what Lutheranism holds as true that may or may not be necessary for salvation. And which Lutheran denomination retains the proper doctrine...?
Jeff, you'd have to get a whole lot more riled than that before you came across as inflammatory. Inflammatory is just not your habit. Besides, you're well within the area of "questions you're bound to ask".
Starting with the least theologically important question first:
Q. Which Lutheran denomination retains the proper doctrine?
A. The one(s) still holding to the original Tradition of the church, that handed down by Christ through the apostles.
Q. What is necessary for salvation?
A. Christ is necessary for salvation. Doctrine, in its best sense, is a full life-giving knowledge of God and his kingdom. Unfortunately, "doctrine" often becomes a set of propositions to be memorized whose content (in theory) could convey some knowledge of God and his kingdom if only people weren't so busy mistaking doctrine for salvation. It would be like mistaking the nutrition label on the can for a nourishing meal. (See, it says right there, "100% iron, 100% calcium ... and I already read the label so I'm set! I read it twice, so I'm more nourished than you!") What Christ said about Scriptures could easily be said about doctrine: You eagerly search them because you think that by them you have eternal life. These are they that testify about me, yet you refuse to come to me and have life.
There are all kinds of things that are true (Lutheran doctrines, Roman Catholic doctrines, doctrines of all kinds of other groups too numerous to name) that are not "necessary for salvation". There are things that are true about God, but knowing them is not "necessary for salvation". If doctrine isn't necessary for salvation, then what is the purpose of doctrine? To bless us through knowledge of the Holy One. I have often asked myself, "Is there really any other blessing besides God?" To know God is to have peace and patience and perseverance. To know God is to have the fullness of love. To know God is to have complete freedom from fear. To know God is to have all wisdom. To know God is to be joyful. What good thing is outside of him? That is what doctrine is about: there is no higher blessing than God.