There is no obvious relationship between Moroni’s text and Paul’s statement on hope from 1 Corinthians 15, but there is a similar attempt to explain the relationship of hope to our spiritual lives. In Paul we find:
1 Corinthians 15:19
19 If in this life only we have hope in Christ, we are of all men most miserable.
The message in Paul contrasts mortality and post-mortality. What he is saying is that for the Christian, hope relates to the expectations of post-mortal reality. Hope is miserable if it is limited to this life only, for it is painfully obvious that the Christian ideal is no guarantee for a peaceful, gracious life in this world. It is for this reason that Paul says that “if in this life only we have hope in Christ, we are of all men most miserable.” We are miserable because it would be evident that our hope would be in vain; if that hope were limited to mortality. Hope is inherently a principle that looks to a post-moral fulfillment of glorious promises, but understands that mortality might never see them.
This is Moroni’s contrast between hope and despair. If one has hope and looks to the post-mortal blessings of the gospel, then there is courage, and perhaps even some joy in understanding the purpose of our earthly trials. However, stripped of that hope, we find ourselves in despair because we are faced with the reality of this life, and have no vision of any improvement. Moroni further links this type of despair to iniquity. That particular iniquity is the rejection of the gospel, not simply sin. The idea that Moroni is expressing is that if we reject the Savior, then of necessity our hope in the post-mortal life is shorn from us, and we are left with only that earth-bound, fickle, and typically unfulfilled hope that so readily turns to despair.