Hoping Against Hope—And Against Their Own View of 2 John 9

One of the differences you will find among traditional preachers is this: Some argue that all Christians (at least all who are sufficiently mature) who persist in practices believed to be unauthorized in scripture—such as instrumental music in worship—are unequivocally lost. There is no hope for them unless they repent and cease the practice. But [...]

Does 2 John 9-11 prove the traditional doctrine of fellowship?

I have been in correspondence with a respected conservative preacher. We have been exchanging arguments for some time now, but neither of us has persuaded the other. Since he is contending for the traditional view which I am here attempting to critique, I will be addressing his arguments periodically in this blog.
 
[9] Anyone who goes [...]