Often, critics will claim that early Mormon theology was reflective of Modalism. One of the purported "proofs" of such is the claim that Joseph Smith said he only saw Jesus Christ in the 1832 account of the First Vision, and, they argue, Joseph believed that the Father, Son, and Spirit were not three persons but modes of a single person. However, this is false. Firstly, Joseph Smith never said the only saw Jesus Christ in the 1832 account, so that is a logical non sequitur. Secondly, Joseph’s comment that “the Lord opened the heavens upon me and I saw the Lord" is not a proof of Modalism and/or Joseph claiming only Jesus was present (see this page); indeed, Joseph’s comment at the beginning of the account that he received a testimony from on high reflects language in the Book of Mormon and the Doctrine and Covenants of the person of the Father, so is actually implicit evidence of two heavenly personages being present in the 1832 account.
Perhaps a killer blow to the charge of Modalism being the Christology of the 1832 account, however, is none other than the words of Jesus Christ Himself, where there is clearly a distinction of the persons of the Father and the Son:
[B]ehold, and lo I come quickly as it is written of me in the cloud clothed in the glory of my Father.
The glory that the person of Jesus Christ possesses when he comes again in glory (his Parousia) is not his own, but the glory given to Him by the Father; there would be no such distinction if they were one and the same person.
Suggested Reading
David Paulsen and Ari D. Bruening, “The Development of the Mormon Understanding of God: Early Mormon Modalism and Other Myths”
