The most wondrous and most annoying thing about Luther is his approach to the freedom of a Christian. It is wonderful, for it focuses one completely upon Christ and what He has done. It is annoying, for it means I cannot win many practical debates by simply saying, "You CAN'T do that." Instead, I must take the more difficult task of, "My friend, why would you want to do that?"
I bring this up as we have Dr. Cameron MacKenzie lecturing on Luther and his reforms to worship at our District Workers Conference. To sum... Luther thought that we were free to change the liturgy in service of the Gospel (and that "in service of the Gospel" is key), but Luther also clearly teaches that it is a stupid and foolish use of freedom to go off and do something different from everyone else simply to be novel... because being novel fundamentally isn't serving the Gospel.