The following quotation by W. H. Littlejohn might not be new to some, but it was for me. Please notice that he speaks on behalf of S. D. Adventists, clearly explaining what the denomination believes, and does NOT believe. Also, it is the only quotation I know of that articulates the rationale why the Father "should have antedated Christ in his being" (clearly rejecting the "incarnational Sonship" theory). Then Littlejohn insists that SDA's only "hold to the distinct personality of the Father and Son", rejecting the notion of "distinct personality" for the Holy Spirit. Finally, Littlejohn references the "Fundamental Principles of S. D. Adventists" as supporting everything he has just explained. This is an important point, considering there are some who explain the "Fundamental Principles" to be "neutral" regarding the Trinity, and therefore could be accepted by Trinitarians and non-Trinitarians alike.
Advent Review, April 17, 1883 p. 250
96.—CHRIST NOT A CREATED BEING.
Will you please favor me with those scriptures which plainly say that Christ is a created being? J. C.
ANS. You are mistaken in supposing that S. D. Adventists teach that Christ was ever created. They believe, on the contrary, that he was "begotten" of the Father, and that he can properly be called God and worshiped as such. They believe, also, that the worlds, and everything which is, was created by Christ in conjunction with the Father. They believe, however, that somewhere in the eternal ages of the past there was a point at which Christ came into existence. They think that it is necessary that God should have antedated Christ in his being, in order that Christ could have been begotten of him, and sustain to him the relation of son. They hold to the distinct personality of the Father and Son, rejecting as absurd that feature of Trinitarianism which insists that God, and Christ, and the Holy Spirit are three persons, and yet but one person. S. D. Adventists hold that God and Christ are one in the sense that Christ prayed that his disciples might be one; i. e., one in spirit, purpose, and labor. See "Fundamental Principles of S. D. Adventists," published at this Office. Price, 4 cts. (W. H. Littlejohn, p. 250)