Mormon has already made the point that “faith and hope [are] vain” except for “the meek and lowly in heart.” This is not a new caveat in Mormon’s discussion. Verses 5–13 discussed the relationship of actions to the motivation that underlies them. That concept is essential to his current argument. To lay hold of all good things, one must have faith, which involves action. Those actions can be good only if our intentions are good. Purity of intent comes from being humble before God so that our actions are in accord with the path he has laid out for us.
Mormon next links faith and hope to charity. He has moved from the external action of faith to the internal motivation of hope. Now that he is dealing with the person’s heart and the need for humility, he can link charity to those concepts as the external evidence of internal humility. Thus, the progression of concepts moves from external (faith manifest in action), to the internal (the hope that motivates us to a specific type of faith), and finally a return to the external (in charity—the external actions of one who is internally humble before God). This is the reason that we are “nothing” without charity. Charity witnesses the change in our hearts that moves us toward becoming like God. If we have not achieved such love (in at least some degree) we are not on the correct path. “Every good thing” will elude our grasp because we are not meeting the requirements for achieving it.
Reference: The idea that one is nothing without charity echoes 1 Corinthians 13:2: “And though I have the gift of prophecy, and understand all mysteries, and all knowledge; and though I have all faith, so that I could remove mountains, and have not charity, I am nothing.”