I don't know, nor do I claim to know. I'm not getting involved in the argument about who defines Christianity; I just noted that the religion is defined by its doctrine, and by what the key tenets of the faith involve. If as fr0d0 suggests, the Nicene Creed was the agreement of the doctrine, then the Nicene Creed is what we should go by.
People can think they are "Christian" all they want, just as people can think they aren't "gay" all they want, but thinking (or believing) something doesn't make it true.
People can think they are "Christian" all they want, just as people can think they aren't "gay" all they want, but thinking (or believing) something doesn't make it true.