What at least one reference has to say about who is a Christian.
Range of definitions of "Christian:
There are also many distinct definitions of the term "Christian" (pronounced 'kristee`ân). Different people have defined a "Christian" as a person who has:
Heard the Gospel in a certain way, and accepted its message, or
Become "saved" -- i.e. they have trusted Jesus as Lord and Savior), or
Been baptized as an infant, or
Gone to church regularly, or
Recited and agreed with a specific church creed or creeds, or
Simply tried to understand and follow Jesus' teachings, or
Led a decent life.
Following these different definitions, the percentage of North American adults who are Christians currently ranges from less than 1% to about 75%.
Within a given denomination or wing of Christianity, there is usually a consensus about who is a Christian, and who is not. However, there is often little agreement among members of different faith groups on a common definition of "Christianity."
Visitors to this web site send us many E-mails daily that comment on its contents. About 80% are positive. But among our negative and sometimes angry Emails, and occasional death threat, the two most common topics are the proper definition of "Christian" and our use of BCE and CE format to identify years instead of BC and AD.
What people can agree on, and what they cannot:
With a bit of effort, one can sometimes collect a random group of adults and have them reach a consensus on a definition of:
Who is an Evangelical Christian, or
Who is a Roman Catholic, or
Who is an Eastern Orthodox believer, or
Who follows the Historical Protestant faith, or
Who is a Pentecostal, or
Who is a Mormon, or
Who is a Jehovah's Witness,
etc.
But it is probably impossible to have any large group of adults reach a consensus on precisely who is a "Christian," and who is not.
There are on the order of 1,500 denominations, para-church organizations, and other groups in the U.S. who consider themselves to be Christian. 1 Added to this are thousands of independent Christian congregations which are not affiliated with a denomination. One could assemble a random group of adults and ask each individual to sort the 1,000 groups into two piles: those which are "truly" Christian, and those that are not. In some cases, an individual will select their own faith group as the only truly Christian denomination, and define all of the other 999 as sub-Christian, quasi-Christian, or non-Christian. Other individuals might say that all 1,000 denominations are Christian. Most likely, a given individual will select most of the 1,000 groups as Christian, and reject the others. There is no possibility of reaching a common definition which would identify which groups are "truly" Christian.
Source