The appearance of Christ in the New World constituted for Mormon a proof positive that God fulfills his promises. The prophets promised that the Atoning Messiah would come. He did. For Mormon, there is no room for doubt that the record of the ancestors is correct. This Atoning Messiah did come, and therefore faith is God is justified for God fulfills promises.
Even though the appearance of the Atoning Messiah altered the nature of faith in the sense that the promise was no fulfilled, it still did not remove the need for faith. Even knowing that the Savior had come, man must believe in his name to lay hold on all good things. For Mormon, the foundation of faith has shifted. In the pre-Messianic-appearance world, faith rested on the foundation of prophetic promise. In the post-Messianic-appearance world, it rested upon the foundation of that very appearance. That reality shores up the new requirements of faith, that we believe in the effectiveness of Christ’s words to lead us to the good things of God.