There's no one source which any Scotsman claims defines a Scotsman, though, whereas pretty much the core part of the definition of Christianity is following the teachings of Christ (it's in the name!), which the vast majority of bigots-who-call-themselves-Christians certainly don't.
That's still a tough one though. Do we stop at just the words of Jesus, or do we include the teachings of the apostles? And if we include the apostles, what about the Catholic 'continuation' of that? Or what about reinterpretations by self-proclaimed prophets that are part of the many fascinating, sometimes scary, and sometimes sizable 'sects'?
