Of the thousands of religions in our world today, only three are monotheistic (believe there is only one God): Judaism (2000 B.C.), Christianity (A.D. 30), and Islam (A.D. 600). Of these three, only one believes God is a Trinity (a Tri-unity): mainline Christianity. Three groups, who claim to be Christian, do not believe in the Trinity as being three manifestations of one God: Jehovah’s Witnesses, Mormons, and Unitarians.
A Jehovah's Witness brochure entitled "Beliefs and Customs that God Hates" includes the Trinity, saying: “Is Jehovah a Trinity - three persons in one God? No! Jehovah, the Father, is "the only true God." (Jn. 17:3; Mk. 12:29) Jesus is His firstborn Son, and He is subject to God. (1 Cor. 11:3) The Father is greater than the Son. (Jn. 14:28) The Holy Spirit is not a person; it is God's active force. Gen. 1:2; Acts 2:18.” Without taking the time in this post to correct their obvious interpretive errors, I will just say that it is interesting that they have chosen to claim “Jehovah” as the one true God, when the name, Jehovah, appears only four times by itself in all of the Old Testament (Ex. 6:3; Ps. 83:18; Isa. 12:2; 26:4). In the KJV, the same Hebrew word, יְהֹוָה (Yhvh), is translated “I AM” in Exodus 3:14, and “LORD” nearly 8000 times, where it refers to the pre-incarnate Jesus (see my blog dated February 7 – “JESUS IS JEHOVAH / LORD / GOD!”).
While Mormons say they believe in the Trinity, their definition of the Trinity differs from mainline Christianity. Mormons believe that the Godhead is made up of three distinct beings who are "one in purpose" but not in being. Jesus is affirmed as Son of God, but not God himself. He is a created spirit. In the Mormon Doctrines and Covenants, Section 130 states: “22 The Father has a body of flesh and bones as tangible as man’s; the Son also; but the Holy Ghost has not a body of flesh and bones, but is a personage of Spirit. Was it not so, the Holy Ghost could not dwell in us.” LDS Apostle Bruce McConkie wrote: “Although it is not found in any of Mormonism's Standard Works, an expression which precisely defines the LDS teaching that men can become Gods was coined by fifth LDS President Lorenzo Snow. In June of 1840, Snow declared, "As man is, God once was; as God is, man may become. Thus those who gain eternal life receive exaltation…. They are gods.” (Mormon Doctrine, p. 237)
“Joseph Priestley, one of the founders of the Unitarian movement, defined Unitarianism as the belief of primitive Christianity before later corruptions set in. Among these corruptions, he included not only the doctrine of the Trinity, but also various other orthodox doctrines and usages (Earl Morse Wilbur, A History of Unitarianism, Harvard University Press 1952, pp. 302-303).” While not officially included under the heading of Unitarianism, Oneness Pentecostalism (also known as Apostolic Pentecostalism or One God Pentecostalism) refers to a grouping of denominations and believers within Pentecostal Christianity, all of whom subscribe to the non-Trinitarian theological doctrine of Oneness.
Genesis 1:1 says, “In the beginning, God (Elohim – noun, masculine, plural – which in Hebrew means three or more) created the heaven and the earth.” Deuteronomy 6:4 says, “Hear O Israel: The LORD (Jehovah – noun, masculine, singular) our God (Elohim – noun, masculine, plural – which in Hebrew means three or more) is one LORD (Jehovah – noun, masculine, singular).” New Testament references to the Trinity: Matt. 3:16-17; 28:19; Jn. 14:16-17; 2 Cor. 13:14; etc. The Father is God (Rom. 1:7). The Son is God (Rom. 9:5). The Holy Spirit is God (1 Cor. 5:3-4).
“For in Him (Jesus) dwelleth all the fullness of the Godhead bodily” (Col. 2:9)!