Let's do what every teenager does while speaking to the congregation for the first time. We'll explore the dictionary.
Merriam-Webster says: "one who professes belief in the teachings of Jesus Christ"
Dictionary.com says: "of, pertaining to, or derived from Jesus Christ or His teachings: a Christian faith"
Merriam-Webster, or as it was formally known, Webster's Dictionary, the American classic, defining our language in most of our homes, right now, in 2008, says a Christian is "one who professes belief in the teachings of Jesus Christ". Dictionary.com says virtually the same thing.
However, it seems to me that the issue of some is based on the "teachings" part of these definitions, attempting to determine who truly follows the "teachings" of Jesus Christ and who does not, such as Pat Robertson, who is a very good man, one who I believe does his very best to follow Christ, but has determined that members of the Church of Jesus Christ of Latter-day Saints are members of a cult.
It seems that some have desired to more restrictively define the term "Christian" to people who believe in Jesus' words in the Bible in their particular way, preferring to ignore scriptural evidence concerning "works", to accompany faith and grace, as if "works" somehow devalues the importance of the grace of Jesus Christ.
Many of my Evangelical friends point to scriptures such as, "For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast" (New Testament | Ephesians 2:8 - 9) and "For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life" (New Testament | John 3:16).
Those of us members of the Church of Jesus Christ of Latter-day Saints might then counter in the Bible with scriptures such as: "But wilt thou know, O vain man, that faith without works is dead? . . . For as the body without the spirit is dead, so faith without works is dead also" (New Testament | James 2:20, 26), or the story of the man in Matthew 19:16-19 who asked the Savior what to do to gain eternal life and Christ instructed him to do many things (or "works").
Finally, we would likely quote the prophet Nephi who wrote in the Book of Mormon: Another Testament of Jesus Christ, "For we labor diligently to write, to persuade our children, and also our brethren, to believe in Christ, and to be reconciled to God; for we know that it is by grace that we are saved, after all we can do" (Book of Mormon | 2 Nephi 25:23).
This scripture really brings it all together for me. And quite frankly it just makes sense. We should spend our days on this Earth doing good works. However, in the end, we are fallible, mortal human beings that ARE NOT capable of receiving salvation on our own. We are not capable of overcoming death on our own or paying the full price for our sins. Only one person was. Fortunately, in the end, we are saved by the grace of Jesus Christ and the power of his atoning sacrifice where "all men are saved from death, hell, the devil, and endless torment" (The Purifying Power of Gethsemane, Bruce R. McConkie). There truly is no other way!
Of course, this begs the question, "If we are saved by the grace of Jesus Christ, then why do works matter, where do they get me?" This is yet another discussion. Suffice it to say, this is why there must be degrees of salvation, or "levels" of heaven, not simply a black and white heaven and hell. In fact, at the risk of completely invalidating everything I've written here due to this source, I believe that Yoda was speaking truth when he said: "Only the Sith speak in absolutes". (Hey I'm good with that quote because: "If there is anything virtuous, lovely, or of good report or praiseworthy, we seek after these things".) Concerning 'degrees of salvation, or "levels" of heaven', see 1 Corinthians 15:40, followed by Doctrine and Covenants 76, then Doctrine and Covenants 131:1-4.
But in the end, who is it that is truly authorized to determine what are the true teachings, or rather, how to interpret the doctrine of Jesus Christ found in the Bible? Who has the authority to speak for Jesus Christ on this Earth? Just as in the Old Testament and in the New Testament, our Father in Heaven and Jesus Christ have given us true and living prophets to interpret and teach the gospel of Jesus Christ to us, his children that he loves so much!
Now, returning to the original question, "What is a Christian?" How do I define a Christian? Do I believe that people not of my denomination, that non-Mormons are all not Christians? No way! One of the finest, truest Christians I know is not a Mormon. Ron McKenzie is the best father and one of the kindest servants of his fellow man that I have ever met. He has probably never read this scripture, but he is a true practitoner of it: "when ye are in the service of your fellow beings ye are only in the service of your God" (Book of Mormon | Mosiah 2:17).
I believe a true Christian is a believer in Jesus Christ who does everything in his or her power to following the teachings of Jesus Christ as far as that person understands those teachings. I am a member of the Church of Jesus Christ of Latter-day Saints, a Mormon, I believe I am a Christian and I am very humbled and thankful for my other Christian brethren and sisters in this world.
It is my testimony that through Christ, after all that I can do, I will be saved by his grace, but that how I choose to use my time, or my "works" serving God rather than mammon, will determine my final estate, for I know that God is a just God. I share these words with you in the name of Jesus Christ. Amen.