To answer this question you have to answer two separate questions. Who are Mormons and who are Christians?
Who are Mormons
The term Mormons is commonly used to identify members of the Church of Jesus Christ of the Latter Day Saints, a group started by John Smith in 1830. That is the easy half of the question to answer.
Who are Christians
To correctly answer the question that was asked, however, you must ask yourself what it means to be a Christian and this term means many things to different people.
The simple definition
One answer is the group of people who believe in Jesus Christ. That definition, however, is not exact enough. After all, the Jewish people and the Muslims also believe in Jesus Christ as a person who lived on the Earth in the past and was a prophet.
To a Jew, Jesus Christ certainly existed, but was a false messiah. They accept none of the New Testament claims about the majority of His life and current status.
Muslims believe in the virgin birth of Jesus from Mary by the command of God, believe He did miracles by God, prophesied, ascended to Heaven, and will come again to battle the anti-Christ. They just reject that He was first God. They also reject the crucifixion and resurrection of Christ since God could never be defeated, and since they reject His sacrifice on the cross, by default they reject that He atoned for mankind's sin on the cross (1 Cor. 1:17-23).
So both of these groups of people believe in Christ, but neither would be considered Christian by any group today.
A bit more careful definition
So what makes a person a Christian beyond believing that Christ existed?
The next extension of the definition provides the clue. A Christian is one who believes in Jesus Christ and has accepted Him as their personal Savior. Most would further say that they should be working toward having Him be the Lord of their lives and receiving and acting on His directions and commands through the working of the Holy Spirit and reading of the Bible. Many would go on and say that a Christian's life should be changed from what it was before by not allowing sin to reign any more in it.
But really, it is not necessary to look at anything but the first part of the definition to answer the question about Mormons and Christianity. After all, the thief on the cross only had to accept Christ as His Savior to be saved. He didn't have time to do any works or allow Him to be Lord in his life since He had no time for that.
So the basic issue that must be answered is this - Who was Jesus Christ? If you are going to accept Him as Savior, what was special about Him that makes Him able to save?
The Christian View of Christ
For a Christian denomination - in any of its various forms - Catholic or Protestant, the answer is easy. God visited the young woman Mary and divinely created life in her, while she remained a virgin, espoused to Joseph. The concept of the Trinity provides God in three persons, commonly termed - Father, Son, and Holy Spirit, eternally existing yet acting united in one purpose. The term Son should be understood as an identification due to His interaction with humanity and not as the Son of the Father. Part of the trinity which we refer to as the "Son" set aside His divinity for a time and lived as Jesus as a human.
Since sin passed down through man to each generation from Adam on, Jesus was unique in two ways. He didn't have the curse of sin to start with since He was not of the seed of man and He was the offspring of both God and man since God was His father and Mary was His mother. This allowed Him to be a truly sinless sacrifice when He was crucified on the cross to bear our sin. He had lived a perfect and sinless life, being full of the Holy Spirit, and He started sinless due to His parentage. When He was crucified, He was truly the perfect sacrifice, given once for the sin of mankind to reconcile God to mankind. He is unique in earthly terms.
For a Christian, accepting the sacrifice of Jesus on the cross is the only means of salvation. At His resurrection, He led all those souls who were righteous and living in paradise to heaven with Him, and He then took His rightful position beside God with His fully restored power as God.
It is this view of Jesus Christ that must be compared with that of the Mormon's to answer the question of whether or not they are Christians.
The Mormon view of Christ
The Mormon view is different from this in two ways. The first, and most important, deals with the nature of God and thus with what Jesus was to start with. The second deals with methods of salvation.
Since the second difference is easier to dispose of, let me briefly say that in the late 1830s, John Smith added baptism by proxy as a means of saving people who had never joined the LDS church in order that they might be saved after death. The Catholic church doesn't get off scot free about this either, as they introduced the concept of a purgatory where you could strive to achieve the holiness and purity you needed to reach heaven after death if you weren't quite there when you died. Gifts to the church and subsequent prayers by priests for your souls helped thus helping to usher in Protestantism. Neither the Mormon teaching of baptism by proxy nor the Catholic teaching of purgatory is in harmony with scripture and most Protestant denominations would roundly reject anything that any living person could do for someone who had died to influence God's final judgment on them. (Hebrews 9:27). Protestants wouldn't have problems with Catholics being Christians, however. The only issue Protestants would have would be in the hope after death that purgatory or proxy by baptism provides. These would be rejected as being out of harmony with Christianity.
The primary objection of including Mormons as Christians, however, comes from the nature of Jesus Christ himself, and indeed, their view of God.
Originally, Mormons believed in a doctrine of original sin, although young children could not sin themselves. As time progressed, they developed a theory that God was once a man who had ascended to the top of the heavenly hierarchy after death. Any human could become a god if he was perfect enough. He was God simply because He was smarter than the rest. As time continued, God became Adam and thus the father of the human race. Other perfect humans could found dynasties on other planets once they died and took their place in the grand scheme of things. After His death, He then descended again as Jesus through Mary and the cycle repeated. Most of these ideas eventually were discarded although they are still held by certain fundamental Mormon groups.
The current views of LDS groups reject the concept of original sin. They believe that Jesus is both the Jesus of the New Testament and Jehovah of the Old Testament. God and Jesus are not co-equal. Jesus is subordinate to God. God is viewed as having lived a mortal life, died, was resurrected, ascended along with a Heavenly Mother, had spirit offspring - the first of which was Jesus. This generation of spirit offspring would be what the Bible refers to as angels which is counter to Catholic and Protestant beliefs. A competition between Jesus and Lucifer occurred to see who would be the earthly Jesus through Mary and Jesus won. Thus there is no concept of a virgin birth either, and Jesus, far from being God Himself, is reduced to the rank of angel.
Thus the bottom line becomes this - is the Jesus Christ that you have to believe in and accept as Savior to be called a Christian the same to a Catholic or Protestant Christian and to a Mormon. Clearly, the Jesus who actually walked on earth is the same one. But the reality of who He was before and who He is now is totally different. It is God sacrificing Himself for man that is the key to Christianity. There's just the Trinity. We don't get to become Gods ourselves and indeed were created lower than the angels but will judge angels. Angels are created beings, just like us, the seraphim, cherubim, the creatures around the throne, and the rest of life we see around us. They aren't some ascended being who might get to be God one day. Lucifer thought he might get to be God one day and look what happened to him.
I think it is pretty clear that the differences in the belief systems in the history of Jesus before His birth to Mary and His life and position afterwards point to clear differences between the two religions and since it is the key to salvation, the differences are significant. It isn't enough to believe in the same words but change the definition of the words to suit you and deceive yourself into thinking you are something you are not. To accept Christ as Savior, it has to be the same Christ that the Bible describes - God Himself. An angel isn't going to get you to heaven.
It is not for nothing that almost 2,000 years ago Paul warned about adding or altering doctrine, even if directed by an angel (Gal. 1:6-12) as Mr. Smith said he was. Just putting the name of Jesus Christ in your denomination is insufficient to meet the test. God is faithful about laying out both in word and type what He is going to do in the future. The prophecies that He make come true and can be verified. The religious changes that He prophecies come true and can be verified. There are many scriptures pointing out that Christ would come and die for our sins, from the garden of Eden through Isaiah and beyond. It was prophesied, it happened, and the old priesthood and covenant were made of no effect. There were no other doctrinal changes forecast in the Bible. There were only warnings to not let its teachings be changed by anyone - either man or angel.
Will there be changes to come? Of course. The millennial period will have Christ returning to earth to set up a theocracy and all world religions will be replaced with a perfect worship of God. Some religions in the world are completely at odds with Christ. Some are partially right and partially wrong. Even Christianity has, I am sure, gotten some things wrong that God will straighten out among each denominations practices. But even this next major worship change is prophesied in the Bible.
There is nothing in the Bible to hint that, oh, say 1900 years after I've set up Christianity I'm going to change things all over again and incorporate Old and New Testament rituals together and call that the new normal and completely blow away the doctrines of Trinity, angels, and man that I have established in my written word for over several millenniums. The only thing that is prophesied to come is the rapture of the church, a tribulation period coupled with a great falling away, and the return of Christ victorious to set up the millennial reign (2 Thess. 2). You can be assured that His doctrines remain intact and His plans remain secure. Don't go to sleep and trust in God's long range plan.
- http://en.wikipedia.org/wiki/Mormonism_and_Christianity and
- conversations with Mormons.
Where the difficulty lies
One problem for many who are outside looking into both Mormonism and Christianity is the nature of the people themselves. The Mormon church is very big on good works. They have to be because in order to reach the perfect state needed to rule your own planet, you need to be baptized in their church and confirmed, follow Christ's teachings, be made a priest, be endowed (prepared to be a king in the life to come) and of course, to do good works in some approved order.
For a Christian, good works should follow naturally after accepting Christ as Savior and Lord, but we recognize that works do not save, salvation does not depend on the husband (in the case of a wife) but solely upon Christ, and that there are no other requirements that are needed like baptism, confirmation, being declared a priest by the powers that be, or endowment. Salvation is by Christ, and Christ crucified - period.
But the good works are important to Mormons. An outside person who doesn't worry about theology is easily led to believe that Mormons are more Christian than Christians simply due to their works and neighborliness. Sadly, good works don't get you to heaven. When the entire salvation experience is based on false beliefs, then it doesn't matter how good you are. You have based your salvation on a lie. There are many other religions in the world whose adherents also do good works. That doesn't make them Christian either. Insofar as they do more good works than us, it gives us a target to shoot for, although for a Christian Jesus should always be our ultimate example in who we pick to emulate.
Should Christians be better? Absolutely. I personally think that God is disgusted with religion and Christianity is certainly up at the top of His disgust list. When Jesus Christ walked the earth, His only real complaints about people were directed at the religious leaders of His day - the Pharisees and the Saducees, specifically. Even the woman taken in adultery was only told to go and sin no more after Christ pointedly asked the religious people who brought her to Him where the man was who was with her and suggested that the person who hadn't sinned among them should cast the first stone.
So I suspect He would have harsh words for Christians today as well - myself included. We should all do better than we have been doing. We should all seek to be filled with the Holy Spirit at least to the level that Paul had. With that indwelling presence, we should be full of the fruit of the Spirit (Gal. 5:22-23) and exercise the gifts of the Spirit as He directs (1 Cor. 12:7-11). We should exercise any ministering gifts we have (1 Cor. 12:28-31). We should witness more. We should stand up against evil more often. We should help others more freely. We should give financial and material assistance where we can to help the poor. We should fully put down sin and iniquity in our own lives and resist temptation. We should eliminate the fracturing of the faith that started with Martin Luther and has continued as the various denominations have branched off over the last century or two into many different streams for reasons that are really pretty unimportant. In all of these things we are failing to a greater or lesser extent.
In many cases, the Mormons are being "better" people in the eyes of the world than we are. That is to our shame, but it doesn't make the Mormons Christian.