C.S. Lewis, writing to a Roman Catholic, "The real reason I cannot be in communion with you is ... that to accept your Church means not to accept a given body of doctrine but to accept in advance any doctrine that your Church hereafter produces."
I have no reference for this quote, and while I don't particularly want to be responsible for disseminating a C. S. Lewis quote that isn't a C.S. Lewis quote (see previous post on the Luther quote that wasn't), it has been sitting on my desktop for weeks now and I can no longer resist posting it. What a classic!