Wouldn’t we love for someone to tell us plainly and perfectly how to judge if something is good for us or bad for us? Here it is. There is probably no simpler, clearer explanation in all the world’s literature than these lines from Mormon.
Verse 5. We can know people by their works. If their works are good, they are good.
Verses 6–10. An evil man cannot do good, or at least anything that will do him any good because, if the motives of his heart are not right before the Lord, “it is not counted unto him for righteousness.” But we should also remember that we must be careful not to presume that we know another person’s thoughts or the intents of his or her heart. For “there is none else save God that knowest [our] thoughts and the intents of [the] heart” (D&C 6:16).
Verse 11. One of the most effective and favorite forms of teaching used by the ancient prophets was to illustrate something in human conduct with something in nature. On avoiding hypocrisy and living with integrity, James, the New Testament writer, metaphorically inquired: “Doth a fountain send forth at the same place sweet water and bitter? … So can no fountain both yield salt water and fresh” (James 3:11–12). Mormon later used this same image: “A bitter fountain cannot bring forth good water; neither can a good fountain bring forth bitter water.”
Jesus taught the same idea with the image of a tree: “Every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit” (Matthew 7:17).
The meaning of all these images is given in plain terms by Mormon: “Wherefore, a man being a servant of the devil cannot follow Christ; and if he follow Christ he cannot be a servant of the devil.”
Verses 12–13. There were never plainer words written than these. Here is how we can discern good from evil:
1. All good things come from God.
2. All evil things come from the devil.
3. Whatever is from the devil invites and entices to sin and to do evil continually. If something invites and entices us to love God and to serve him, if it draws us closer to the fulness of the gospel, it is inspired of God.