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One of the most enlightening revelations given to the Prophet Joseph Smith was D&C 76, sometimes called "The Vision." As most revelations given to the prophet, it came as an answer to a question regarding John 5:29. The Spirit opened their eyes to better understand the two resurrections, the resurrection of the just and the resurrection of the unjust? The revelation that followed unfolded the marvelous plan of salvation and revealed the love that our Father in Heaven has for his children and that is made possible through the atonement of his Son, Jesus Christ. All are saved except sons of perdition who make this choice of damnation for themselves. The plan is loving, generous, and all inclusive.
I love the way the Prophet Joseph Smith expressed himself on the topic of this vision,
Nothing could be more pleasing to the Saints upon the order of the Kingdom of the Lord, than the light which burst upon the world through the foregoing vision. Every law, every commandment, every promise, every truth, and every point touching the destiny of man, from Genesis to Revelation, where the purity of the Scriptures remain unsullied by the folly of men, go to show the perfection of the theory (of different degrees of glory in the future life) and witness the fact that the document is a transcript from the records of the eternal world. The sublimity of the ideas; the purity of the language; the scope for action; the continued duration for completion, in order that the heirs of salvation may confess the Lord and bow the knee; the rewards for faithfulness, and the punishments for sins, are so much beyond the narrow-mindedness of men, that every man is constrained to exclaim: "It came from God." (Feb., 1832.)
(Joseph Smith, Teachings of the Prophet Joseph Smith, selected and arranged by Joseph Fielding Smith, p.11)
As wonderful as the plan is, we must still remember that it is a partial revelation of an even bigger picture. Several years after the revelation the Prophet made this statement,
Paul ascended into the third heavens, and he could understand the three principal rounds of Jacob's ladder-the telestial, the terrestrial, and the celestial glories or kingdoms, where Paul saw and heard things which were not lawful for him to utter. I could explain a hundred fold more than I ever have of the glories of the kingdoms manifested to me in the vision, were I permitted, and were the people prepared to receive them. (emphasis added)
(Joseph Smith, Teachings of the Prophet Joseph Smith, selected and arranged by Joseph Fielding Smith, p.304)
The descriptions of the degrees of glory are not totally definitive. There is more information needed to define some of the terms used in the revelation. Several years after receiving the revelation, the Prophet was shown, in another vision, his brother, Alvin, in the Celestial Kingdom (January 21, 1836). He said that he marveled at how Alvin was in the Celestial Kingdom not having been baptized before his death. From this context it appears that the Prophet had the understanding that Alvin would have inherited the Terrestrial Kingdom. Several months after this revelation showing Alvin in the Celestial Kingdom, the prophet had the experience recorded in D&C 110 where he meets with the Savior, Moses, Elias, and Elijah and learns about the sealing power and work for the dead. Through this experience we can see that even the Prophet Joseph Smith was taught line upon line and precept upon precept.