The vision Joseph Smith supposedly received in 1820 when Heavenly Father told him not to join any church since they were all corrupt. Mormons believe it proves that Joseph Smith was a true prophet of God. “The key to a testimony of the gospel is Joseph Smith’s first vision. All that we believe hinges on this account. … The greatest event that has ever occurred in the world since the resurrection of the Son of God from the tomb and his ascension on high, was the coming of the Father and of the Son to that boy Joseph Smith, to prepare the way for the laying of the foundation of His kingdom” (Sharing the Gospel Course Manual, pp. 33f.).