"I am Jesus Christ. I am the Father and the Son." (Ether 3:14)__"...no man knoweth that the son is the Father, and that the Father is the son." (Luke 10:23, JST)
"Modalism is the name given to an ancient heretical teaching that denies that Father, Son, and Holy Spirit are distinct Persons within the one Divine Being or Godhead."  Early Mormonism taught a form of modalism, as is evident in Joseph Smith's retranslation of the Bible (the " JST") and the 1830 version of the Book of Mormon.
As late as 1849, Orson Pratt observed that
"some [Saints]... believed that the spirit of Christ, before taking a tabernacle, was the Father, exclusively of any other being. They suppose the fleshly tabernacle to be the Son, and the Spirit who came and dwelt in it to be the Father; hence they suppose the Father and Son were united in one person, and that when Jesus dwelt on the earth in the flesh, they suppose there was no distinct separate person from himself who was called the Father." 
|Contents _1 In the Book of Mormon_ 2 In the Joseph Smith Translation _3 Popular conception of the Trinity 4 Quotes 5 See also_ 6 Offline resources 7 Notes 8 External links 8.1 Non-Mormon 8.2 Mormon|
In the Book of Mormon
"And now Abinadi said unto them: I would that ye should understand that God himself shall come down among the children of men, and shall redeem his people. And because he dwelleth in flesh he shall be called the Son of God, and having subjected the flesh to the will of the Father, being the Father and the Son — The Father, because he was conceived by the power of God; and the Son, because of the flesh; thus becoming the Father and the Son" (Mosiah 15:1-3, 1830 Book of Mormon).
"No clear distinction is made between the person of God the Father and the person of God the Son in the  Book of Mormon. In fact Jesus is clearly asserted to be both. This is stated most baldly in Ether 3:14: “I am Jesus Christ. I am the Father and the Son.” The Son is repeatedly referred to as the “Eternal Father.” (1 Nephi 11:21, 13:40; Mosiah 16:15; Alma 11:37-38). And so we read, for example, “behold the Lamb of God, yea, even the Eternal Father,” (1 Nephi 11:21), and “the Lamb of God is the Eternal Father and the Saviour of the world.” (1 Nephi 13:40; cf., Mosiah 16:15 and Alma 11:37-38)." 
"Prior to the incarnation the title Eternal Father is used almost exclusively of Jesus (1 Nephi 11:21, 13:4; Mosiah 16:15 Alma 11:38-39). The only exception is the Abinadi’s speech in Mosiah 15:1-7 already mentioned, where the Father and the Son together are the Eternal Father, but that statement appears in the context of explaining how the Eternal Father became the Son by taking on flesh." 
In the Joseph Smith Translation
The Joseph Smith Translation of the Bible teaches the following in Luke 10:23:
"...no man knoweth that the son is the Father, and that the Father is the son."
Popular conception of the Trinity
Mormons usually mistake the doctrine of the Trinity for modalism. You might hear the following in a correspondence with a Mormon: "We don't believe in the Trinity, because we believe that the Father, Son, and Spirit are three different persons." This is ironic, because the Trinity teaches that God is one God-being in three persons.
See main article: Trinity
- "The Book of Mormon tended to define God as an absolute personage of spirit who, clothed in flesh, revealed himself in Jesus Christ."
- "In the Book of Mormon, we see a conscious attempt to reconcile trinitarian and Unitarian controversies raging in Joseph's environment but which seem anachronistic as ancient musings when compared to biblical and early Judeao-Christian thought. Joseph was attempting, I submit, just as Janice, to sort things out. In later years he reversed his earlier efforts to completely 'monotheise' the godhead and instead 'tritheised' it."
- Mormonism and the Nature of God: A Theological Evolution, 1830 - 1915, by Kurt Widmer (McFarland & Company, 2000) ISBN 078640776X
- ↑ 
- ↑ Quoted by Boyd Kirkland in "Jehovah As Father: The Development of the Mormon Jehovah Doctrine". Sunstone 9.2.
- ↑ 
- ↑ 
- ↑ Thomas Alexander (LDS), The Reconstruction of Mormon Doctrine, p. 25 
- ↑ Boyd Kirkland, “An Evolving God,”. Dialogue: A Journal of Mormon Thought 28, no. 1 (Spring 1995), p. v.
- Jesus and the Father. The Book of Mormon and the Early Nineteenth-Century Debates on the Trinity, by Clyde D. Ford
- Joseph Smith’s Modalism: Sabellian Sequentialism or Swedenborgian Expansionism?, by Ronald V. Huggins
- Jehovah As Father - The Development of the Mormon Jehovah Doctrine, by Boyd Kirkland
- Does the Book of Mormon Teach Mainstream Trinitarianism or Modalism? (PDF), by Barry R. Bickmore (Mormon)
- The Development of the Mormon Understanding of God: Early Mormon Modalism and Other Myths, by Ari D. Bruening, David L. Paulsen (Book review)
- Review: Mormonism and the Nature of God
- Fatherhood and Sonship of Jesus Christ, by Robert L. Millet
- Melodie Moench Charles and the Humanist Worldview, by Ross David Baron - Review of "Book of Mormon Christology", New Approaches to the Book of Mormon: Explorations in Critical Methodology
- God Himself, by Kathryn Lynard Soper
- The Book of Mormon’s Doctrine of Deity, by Bruce Nielson
- Review: Mormonism and the Nature of God Kurt Widmer