one important controversy is simply the definition of the christian or catholic church. to some degree this controversy comes from the nicene creed with its words "one holy catholic and apostolic church" which means "universal" church. many denominations believe that all denominations are part of a world-wide christian church and think that the most important thing is the "common faith" and not a common organisation or tradition. ("common faith" means "the faith that is the same". the word "common" does not mean "ordinary" in this sense.)