The question "Are Mormons Christian?" is a meaningless query until you define precisely what you mean by "Christian."

            My professional training is in linguistics and law.   Both are areas where words and their meanings are crucial.

            The word "Christian" is a label, and thus it has all the advantages and disadvantages of any label.   The fundamental problem with labels - although they are very convenient - is that we humans tend to think (quite unjustifiably) that if we can find the proper label for something, the label brings an understanding of that thing's essence.   This is not true.   Labels have no such power and contain no such knowledge or information.   Inferences drawn from labels may be correct, but just as likely may not be correct.   That is, we "read into" the thing characteristics that belong to our definition of the label, but not necessarily to the thing we are labeling.

            One great fallacy made by many people when using a label (or defending their use of it) is to rely on a definition that they find for the label in a dictionary.   And usually they pick the one definition that supports their own use of the label.   That is the first mistake - being selective and insisting that the definition that supports their argument is the only correct one.   The second fallacy lies in a misunderstanding of what the purpose of a dictionary is, and how it is made.   A dictionary (at least in its listing of definitions) does not pretend to be a divine authority, like the Bible, to be relied on as ultimately correct.   Rather, a dictionary is simply a collection of how words (labels) are used by various speakers of the language.   (Remember the schoolboy taunting the schoolteacher, insisting that " 'ain't' is so a word! - it's in the dictionary!"?)   Some of the usages listed in the dictionary may be poor, inaccurate, or unjustified.   But they are listed in the dictionary because many people use the word in that way.   The dictionary is correctly cited as authority only to prevent us from using words in ways not generally used by educated speakers and writers of the language.

            There are dozens of possible definitions of "Christian," (that is, ways in which people use the word) even in addition to those in the dictionary, and they range all the way from very broad ("a Christian is anyone who tries to live his life by the teachings of Jesus") to very, very narrow ("a Christian is someone whose views and beliefs about Jesus Christ are exactly like mine").  

            Whether one is justified in applying any label to any person or thing depends on the definition you are using, how precisely you define the label, and whether your definition is clear and acceptable to your audience.   If you and your audience have differing definitions in mind, then you will think you are arguing about the object of your label (e. g., the Mormons) when you are really arguing about two differing definitions.

            I think most Christians today who are quick to label Mormons as not Christian generally overlook the fact that the earliest followers of Jesus would probably not qualify under their definition of "Christian," either.   Those early Christians did not accept the Nicean Creed, because that only developed several centuries later (after much debate and by a fairly narrow vote; all the negative votes, of course, having been cast by devout Christians, who were then labeled "heretics").   There was no agreement during the first few centuries on the nature of Christ, the scriptural canon, and many other doctrinal matters, which were only decided much later.   They did not even call themselves "Christians" - the term was not generally used for Jesus' Jerusalem followers, but was invented by the heathen population of Antioch to refer to the Gentile Jesus-followers in Antioch.

            Before asserting to a Mormon that Mormons are not "Christian" one ought to first define precisely what definition one is using.   I suspect that the definition (in the minds of those asserting that Mormons are not Christian) would be something like:   "A Christian is someone who ascribes to the doctrines of any of the churches tracing themselves directly to the Apostles."   Once you enunciate your definition, you are merely stating a tautology, since the Mormons freely admit that they do not ascribe to such doctrines, because they believe they are false.   And that it was the falsity of those traditional doctrines which required a "restoration" through Joseph Smith.

            If you assert that Mormons are not Christian, that also implies that you have the only valid definition, and that you (and your co-believers) are the only ones who have a right to define the word.   That is not the way language works.

            Who can claim the exclusive right to define any label for all speakers of the language?   No one.   Not even those who claim a label as applying only to them.   Any other view would be absurd, and leads inevitably to absurdities.   But that is exactly what many groups do.   Christians insist that they have the exclusive right to pass judgement on everyone's use of the term "Christian." And most do not want to allow Mormons to apply the term to themselves.

            Ultimately, I think one should ask, before trying to convince the Mormons that they are not "Christian":   What am I trying to accomplish here?   If you want to convince the Mormon to rethink his beliefs and examine them, then telling him that he is not a Christian accomplishes nothing but cause resentment.   He already knows that he doesn't believe exactly the same as you or the traditional Christian churches.   That is the whole point of Mormonism.   In fact, the Mormons think that they (the Mormons) are the only "true Christians."

            The whole problem is an example of what logicians sometimes call "The Fallacy of the True Scotsman":

            MacDougal was arguing with MacDuff, claiming that "no true Scotsman puts sugar on his oatmeal!"   MacDuff reminded MacDougal that Angus MacGregor, the Lord Mayor of Edinburgh, head of the MacGregor clan, whose ancestors had fought at Bannockburn, does, indeed, put sugar on his oatmeal.   "Which shows, " said MacDougal triumphantly, "that MacGregor is no true Scotsman!" (See http://www.infidels.org/news/atheism/logic.html#scots )

            A few years ago a man who claimed to be Christian told me in all seriousness that Pope John Paul was not a Christian, since Catholicism is not the true Christianity.   That strikes me as absurd.

            The Mormons actually have the same problem with the word "Mormon."   The Utah church thinks they own the word, and that therefore they have the right to define who is a real Mormon.   It usually comes up when some polygamous group is in the news, such as the FLDS, the "fundamentalist Mormons."   The press release from Salt Lake church headquarters usually says, "They are not 'Mormons'"   The implication is that the only real "Mormons" are those members of the church headquartered at 50 East North Temple who have the imprimatur of that particular branch of Mormonism, and that nobody else is a "Mormon."   It seems to me that the fundamentalists are Mormons, too, in the sense that they also consider the Book of Mormon to be scripture, that Smith and Young were prophets, etc.

            The argument then becomes the more fundamental argument over whose doctrine is correct.   So argue about that, not about the label.

            Actually, there are a number of areas where Mormon and non-Mormon Christians agree about Jesus.   I am neither Mormon nor Christian, but, based on my understanding of Mormonism and of more traditional Christian doctrine, I suggest that these are some of those areas, and one could certainly argue that anyone with these beliefs could be labeled "Christian":

• Jesus is divine and part of the Godhead.
• He is the Messiah promised in the Old Testament.
• The world was created by him.
• He is the "Only Begotten Son" of God.
• He died to atone for the sins of mankind.
• He was prepared from the beginning of the world for his mission of atonement.
• He was bodily resurrected from the dead.
• By his resurrection he conquered death so that all mankind will be resurrected.
• He was perfect and sinless.
• He founded the true church.
• Only believers in him will be saved.
• He will someday return to earth and usher in a period of peace lasting a thousand years, during which he will rule as king.

• Jesus is a separate person from God the Father.
• Jesus is a literal child of God the Father, both spiritually and physically.
• Since we are all spirit children of God the Father, in that sense Jesus is our spirit brother.
• Jesus was married (early Mormon prophets also taught that he was a polygamist).
• Christ's atonement is not effective for certain very grievous sins (this doctrine of "blood atonement" is not mentioned much by modern Mormons)
• The moment of Christ's atonement was as he prayed in Gethsemane, not his death on the cross.
• One should not "worship" Jesus or pray to him, but only to God the Father, in Jesus' name.
• One should not try to develop a "personal relationship" with Christ.
• To be saved, one must not only believe in Christ, but must "obey his commandments" (that is, "works" are as important as "grace")