The entire Plan of Salvation was offered by Moroni as further proof that the God of Whom he spoke was One of miracles. (A miracle, we may understand to be an event or its effect in the physical world deviating from the known laws of nature, or transcending our knowledge of these laws; an extraordinary event brought about by superhuman agency; Mary Baker Eddy, of Christian Science fame, calls a miracle, something that is divinely natural, but must be learned humanly.)
Moroni then introduces Adam, the first man who God created in His own image. Adam sinned and brought death and sorrow onto the Earth which had been created by God for the benefit and blessing of mankind. Adam bequeathed to his offspring his legacy of sin. As a result, God the loving Father of all men, Who Himself is sinless, was separated from His children who as we have noted, were carnal, and who had become sinful and sensual in their fallen state. A redemption from the effects of Adam's Fall must be made that again man and his Father may be united. That Redemption, Moroni points out, came about by the Sacrifice Christ made that man might live, and therein brought back into the presence of God, his Father.
Through the Redemption of all mankind came man's deliverance from an endless sleep which is the grave. When Moroni's father, who was the Prophet Mormon, engraved an address to the Lamanites who survived the Battle of Cumorah, he said-and his words are particularly important here-"Know ye that ye must come to the knowledge of your fathers, and repent of all your sins and iniquities, and believe in Jesus Christ, that He is the Son of God, and that He was slain by the Jews, and by the power of the Father He hath risen again, whereby He hath gained the victory over the grave; and also in Him is the sting of death swallowed up." (Mormon 7:5)
Now that man has been Redeemed from death and the grave by the Sacrifice made by Christ, man is held responsible for his actions here upon the Earth, whether they have been good or whether they have been bad. If he has not repented of sin and still remains in his guilt, he will still be filthy, or unclean, but the righteous shall be happy because of their righteousness, and will go on forever being happy and righteous in that they delight in keeping the commandments of God. That is wisdom. "Behold, the fear of the Lord, that is wisdom, and to depart from evil is understanding." (1 Peter 3:14)