“Given the fact that what makes one a Christian is earnestly trying to follow Christ as our lord…all of us are on a lifelong journey to understand truth…and we are all likely wrong about things as we progress…how can we say that a Mormon, though mistaken, yet earnest is lost?”
This is a great question that needs to be understood. First, I would say you are incorrect in the “fact” you start out with. Earnestly trying to follow Christ does not make one a Christian. Repenting of our sin and placing our faith in Christ and in Him alone is what makes us a Christian. “Earnestly trying” sounds a lot like works and Ephesians 2:8-9 is very clear that salvation is not by works. Real faith includes a decision to follow Jesus, surrendering to Him as Lord, but that is not the same as “earnestly trying.” A true believer earnestly tries to follow Jesus, but it is God’s grace through our faith in Christ that saves us.
Second, your question makes it sound like we gradually become more and more Christian; this is one of the serious mistakes of the Emergent Church. The Bible is very clear that there is a point in time in which we are saved. John 3:3 says we are born again. In verse 18 John says, “Anyone who believes in Him is not condemned, but anyone who does not believe is already condemned, because he has not believed in the name of the One and Only Son of God.” We are either born again or we are not. We are either under condemnation or we are not. I love Romans 8:1 for the believer, “Therefore no condemnation now exists for those in Christ Jesus.” Throughout the book of Acts we see people getting saved and being added to the church. 2:41 says 3000 were added that day. 4:4 says another 2000 were added. 5:14 it says “Believers were added to the Lord in increasing numbers.” I could go on and on. When we are born again and adopted into the family of God through faith we are Christians. Before that moment we are not. We are either “in” or “out.” There is no gradually becoming more and more Christian any more than a woman becomes more and more pregnant (she either is or she isn’t). Once we are saved, we do grow in our relationship, but there is a decisive moment for everyone who becomes a believer, even if they cannot pin point the exact time that did take place (e.g. kids growing up in a Christian home). The New Testament normal time was at baptism (Acts 2:37-38; 22:16; 1 Peter 3:21).
Third, we need to understand that certain doctrines are more important as far as their impact on our life than other doctrines. John 14:6 and Acts 4:12 make it clear that people are only saved through Jesus. 1 John 4:1-3 and 2 Corinthians 11:4, 14-15 lets us know that we have to have the right Jesus. Just because someone uses the name of Jesus, that doesn’t mean they have the right Jesus. You could call your dog “Jesus,” but he can’t save you. Specifically, we need to believe that Jesus is God. It is one thing if someone doesn’t fully understand all the doctrinal implications of the person of Jesus at salvation, and quite another for someone to actually reject a cardinal truth about Jesus and still think he or she is saved. The Mormons do not believe Jesus is God. They believe He is a god, but not the one true God. Mormons believe in polytheism, the belief that there are many gods. Polytheism is categorically rejected throughout the Bible including the First Commandment (see also Deuteronomy 6:4). A perusal of Isaiah makes it very clear that there is only one God (see 43:10-11; 44:6; 45:5, 14, 18, 21; 46:9). Salvation is also a critical doctrine according to the Bible. Galatians 1:8-9 state that if anyone teaches or holds to any other gospel than the one Paul preached he or she is accursed, damned to hell. This is a very serious indictment. Verse 8 specifically says, “even if we or an angel from heaven should preach to you a gospel other than what we have preached to you, a curse be on him!” Mormons believe the angel Moroni told Joseph “another gospel.” This is the same problem with Islam that claims the angel Gabriel told Muhammad another gospel. Any gospel other than salvation by grace alone through faith alone is a false gospel that won’t save a person. I know this sounds harsh, but God has given us His plan and told us that all other plans won’t work. Notice there are passages of Scripture that specifically state you must believe this or else you are not a Christian. Bottom line is that we have to have the right Jesus and the right gospel. We can agree to disagree agreeably on a lot of doctrines, but not these doctrines. Mormons believe we are saved by Jesus “after we do all we can do.” I just quoted Joseph Smith. “After we do all we can do” is a salvation by works. Nobody actually fulfills this phrase either. No one does “all they can do.” All of us could have done more. This is a hopeless gospel.
Those who want to embrace the Mormons or at least the sincere ones into the fold of the family of God have a good heart. They want them to be saved, which is exactly what God wants (2 Peter 3:9). I wished all Christians had that kind of heart. But wanting to see the Mormons saved by bypassing God’s clear instructions actually thwarts their chance of salvation. If we think they are already good to go, we will not make every attempt to share the gospel with them. Liberal Christianity has made this mistake by embracing universalism. I had the privilege of seeing a good friend of mine named Jeff come out of Mormonism and embrace the true Jesus, rather than the Mormon Jesus who is simply one of many gods and is the brother of Satan (that is what they actually believe). He asked me to come and help him when the bishops of the Mormon Church were going to try to convert him back into the fold. We talked with the bishops for a couple hours and it became very clear to both Jeff and me that they didn’t have a clue to the real gospel. Jeff told me afterwards that he was afraid at first, but his confidence in the true gospel skyrocketed after the confrontation. We dare not water down the gospel to make it more palatable to modern society. The gospel itself is powerful enough to break through all barriers (Romans 1:16).
I hope this helps,