Debate: Mormonism is not a Christian religion
Here's a debate I had where my opponent defended the resolution: Mormonism is not a Christian religion. Since Mormonism has something to do with Jesus, you might think Mormonism ought to fall under the Christian umbrella. But a lot of people think the whole worldview of Morminism is so radically different than traditional Christianity, that it's not even the same religion. It only appears to be so because the vocabulary is the same. Although the words are the same, the meaning is quite different.
Although I'm skeptical myself that Mormonism falls under the Christian umbrella, I thought I'd play devil's advocate in this debate and argue that Mormonism is Christian. I figured it might be a learning experience for me. Here is my opening:
Before we can say that some entity (x) is a member of some category (y), we first have to define y. Pro didn't give us a definition of Christianity, although we might be able to infer his meaning from his arguments.
First, let's look at where this word came from. According to Acts 11:26, Jesus' followers were first called "Christians" in Antioch, presumably by outsiders. The word, "Christian," comes from the word, "christ," meaning "anointed one." It's the Greek equivalent of the Hebrew word, "moshiach," or "messiah." So they likely called Jesus' followers Christians because they were following a messiah, namely Jesus. So a "Christian" is somebody who hails Jesus as the Christ.
With that minimal definition in mind, Mormons are obviously Christians. They hail Jesus of Nazareth as the Messiah.
Perhaps we could be even more specific about the meaning of Christianity. The apostles, after all, had a message about Jesus they were spreading around that included some very basic information they called "the gospel." It was preserved in an oral tradition that Paul tells us about in 1 Corinthians 15:3ff. It includes these facts:
1. Christ died for sins.
2. He was buried.
3. He rose from the dead
4. He appeared to Cephas.
5. He appeared to the 12.
It's a matter of controversy whether the rest of the appearances were part of the original oral tradition Paul conveyed, but those five things, at a minimum, defined what the Christian message was. Mormons believe all five of those things, so they are Christians.
Now, perhaps Pro is defining "Christian" differently than I am. Perhaps he means to equate a Christian with a saved person. But as far as I know, the early Church never defined "Christian" that way. In fact, it is evident in a number of books in the New Testament that there are some people within the Christian church who will not be saved (cf. Matthew 7:21-23, 2 Corinthians 11:13, Galatians 2:4, 2 Peter 2:1, etc.). Although these people are condemned as being false brothers or false apostles, and although the implication seems to be that they are not really part of God's elect, they are nevertheless part of the Christian community, and the New Testament never denies that they are actually Christians.
Any reasonable person should admit that it's possible for two people to disagree on at least some points of doctrine even if both of them are Christians. In fact, it's possible for two people to be saved even if they have doctrinal differences. People differ on whether spiritual gifts are active today, whether the return of Christ will happen before or after the tribulation, whether God predestines a particular group of people to eternal life, etc. So the mere fact that Mormons may be wrong on some doctrine is not enough to say that they are not Christians.
Now let's look at Pro's reasons for thinking Mormons are not Christians.
Mormon scriptures are not the word of God
Granted. However, there have been debates within Christianity on what writings are the word of God. Catholics and protestants disagree on whether the Apocrypha is the word of God. In the first few centuries of the church, there were disagreements over whether the book of Revelation was the word of God. Nobody ever said somebody wasn't a Christian just because they had disagreements over the canon. If believing in the wrong books means that you're not a Christian, then either Catholics or protestants are not Christian.
Mormons believe in false gods
Mormons believe the Father, Son, and Holy Spirit are each God just as Trinitarians do. They just differ on the question of whether they are the same God. Whereas Trinitarians believe they are the same God (though distinct persons), Mormons believe they are distinct beings, which logically entails that they are distinct gods. Now, some Mormons will claim that they are monotheists on the basis of the intimate unity between the Father, Son, and Holy Spirit , but I think that is just a semantical game and shouldn't be taken seriously. Mormons are, without a doubt, polytheists.
But I question whether somebody can be excluded from being Christian on the basis of the extra erroneous beliefs they have. Suppose, for example, that I believe all of the essentials of the gospel, but in addition to that, i also believe in unicorns. Since my belief in unicorns is not a denial of any of the essentials of the gospel, I'd still be a Christian. So, if a Mormon happens to believe in some other god that doesn't actually exist, but they nevertheless believe all the essentials of the gospel, then they're still Christians.
Let's look at 1 Corinthians 8, which Pro brought up. If you read the whole chapter, Paul is saying it's okay to eat food sacrificed to idols because we know there is only one God. But, he says, "Not all men have this knowledge" (v.7), and we should "take care that this liberty of yours does not somehow become a stumbling block to the weak" (v.9). In other words, it's a sin to violate your own conscience (as Paul argued in Romans 14), so we shouldn't eat meat sacrificed to idols if it will lead another person to think it's okay, even though they think idols represent real gods. Paul's advice only makes sense if these others, with weak consciences, are fellow Christians, because why else would they even be concerned about eating meat sacrificed to idols? So Paul is acknowledging the existence of Christians who think there are other gods.
Mormons deny their depravity
Christians differ on the extent of their depravity. You have Calvinists on one extreme who think we are so depraved that we are completely unable to come to Christ unless the Father draws us, and you have Pelagians on the opposite extreme who believe just as the Mormons do, that we are in a state of equilibrium. Between these two extremes, there is every shade of belief. These are doctrinal differences that are, at best, secondary to the core of Christianity which I explained above.
Mormons hold to a false gospel
Mormons pour different meanings into their words than other Christians, and this leads to confusion. Mormons talk about salvation in two different senses--general and individual. By "general salvation," they mean salvation from sin and death by the atonement of Christ. To be saved is to be raised to eternal life, and they believe almost all people are saved in this sense by grace alone. If they're guilty of any heresy, it's in believing too many people will be saved. They are nearly universalists.
By "individual salvation," they mean "exaltation." Exaltation is something that happens to some of those who are saved in the general sense. It is similar to what mainstream Christians think of as "rewards," which even good Calvinists will admit are earned by good works (1 Corinthians 3:14).
Mormons, perhaps, use the word "salvation" incorrectly, but they nevertheless believe in salvation, by the usual meaning of the word, is by grace. The confusion comes in the fact that Mormons usually use the word "salvation" to refer to exaltation rather than in the general sense. But if you just look at the substance of what they believe rather than the words they use to describe it, their belief in general resurrection is equivalent to the reformed belief in salvation by grace alone.
As far as the gospel is concerned, Paul defined the gospel in 1 Corinthiains 15:3ff, and Mormons fully subscribe to what Paul said there.