A frustrating aspect of witnessing to Mormons is their tendency to say they believe just as we do. One of the best ways we have found to show them our beliefs about salvation differ is by showing them the heart test.
Draw on a piece of paper a heart filled with plus signs. It symbolizes the perfection needed to live in Heavenly Father’s presence.
Next draw a heart filled with minus signs. The minus signs represent sin. Keep adding minus signs to indicate all the times we sin. Eventually, the heart would be entirely black with minus signs.
Ask your Mormon friend to describe how the heart filled with minus signs becomes the heart filled with plus signs. They may not have much to say, or they might make a general statement about Jesus. Ask them to be more exact. If you have to help them along, ask if they are talking about Jesus’ atonement. Most will readily agree. You can then state that Jesus’ atonement washed away our sins. Either erase the minus signs or draw a blank new heart. The point you want to emphasize is that Jesus’ atonement took away the stain of sin but it didn’t supply the plus signs.
The plus signs, however, are needed in order to remain in Heavenly Father’s presence. Ask them how they are obtained. Mormons will eventually talk about the good works they do.
When they have gotten to this point, tell them that this isn’t what you believe. You believe you don’t do anything to return to Heavenly Father’s presence. It is God’s gift to you. Tell them you believe the plus signs represent all the good works Jesus did in your behalf!
Jesus wasn’t our substitute only when he was on the cross. He was our stand-in his entire life. Galatians 4:4-5 indicates Jesus came not only to die for us, but also to live for us. “But when the fulness of the time was come, God sent forth his Son, made of a woman, made under the law, to redeem them that were under the law, that we might receive the adoption of sons.”
It is instructive to compare this verse with another one in Galatians. In Galatians chapter 3, Paul states that Jesus, through his death, redeemed us from the curse of the law (see 3:13). If redemption from the curse of the law was all that was needed, Paul could have stopped there. But in the verse quoted above, he returns to the thought of redemption and talks about a different aspect. There he shows that Jesus, by placing himself under the law, redeemed us from the obligations of the law.
He did it by keeping the law perfectly for us. In his Sermon on the Mount Jesus said: “Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.” (Matthew 5:17)
We are now credited with his holiness!
Note how Paul describes Jesus in the following passage. “But of him are ye in Christ Jesus, who of God is made unto us wisdom, and righteousness, and sanctification, and redemption” (1 Corinthians 1:30). Jesus is our righteousness, our holiness, our perfection! His perfect works are the plus signs in our hearts.
They might respond by saying this is also what they believe. There are a couple of different ways you could respond. You could ask them why they didn’t give this answer when you first asked them. Or you could point them to some official LDS statement like 2 Nephi 25:23 (“by grace you are saved after all you can do”) and ask them how to reconcile the two.
Even if they try to recover and say they believe the same as we do, be confident you have made them think – even though most won’t admit it. Even more importantly, you have given them a wonderful witness that Jesus has done everything for our salvation.