The first section of the creed sets affirms a core concept of God that stems from the Jewish Old Testament. It reads:
We believe in one God,Right off the bat, Christianity is identified as a monotheistic faith. One God and no others. This is key to all subsequent understanding of God, especially when considering His attributes.
the Father, the Almighty,
maker of heaven and earth,
of all that is, seen and unseen.
For God to be Almighty, there can only be oneGod is first identified as "Almighty." Most people understand the word God to mean a being that is all powerful. But that also means that God must be a single being. For if God is almighty, then He can have no equal. As a contrast, some later versions of Zoroastianism held to a concept of two beings, one good and one evil, who were equally powerful and locked in a constant state of war.1 But you cannot claim that a god is all-powerful if that god cannot win a fight with his enemy! The fact that the war exists at all shows that the god has limited power; his power cannot govern his foe. The problem would of course get worse with multiple gods, limiting the power of one's god even more as the other gods multiplied.
So, in order for God to be Almighty God, He has to be a single being. This is a straightforward logical understanding of God. Christians believe in one Almighty God (Deut 6:4, john 17:3, 1 Tim 2:5). That means that faiths such as Mormonism are excluded from Christianity immediately. Mormonism holds that many beings can become just as God the Father is now2, making God something less than what the creed establishes.
Mormons also believe that God has progressed through time to become God.3 He wasn't always almighty but he is now. Such a statement is self-contradictory since there is some mechanism (the eternal progression law or function or whatever) that God cannot have dominion over. Instead, He must obey its precepts to become God himself. That again means that the God of Mormonism isn't Almighty.
All of reality depends on the One GodThe next part of that first sentence declares that God is the maker of heaven and earth, whether those things are part of the natural world (seen) or the spiritual world (unseen). All of creation relies upon God for its existence. God didn't need to create the universe, but He chose to do so. This makes God completely without dependence and when He creates, He creates out of nothing (Gen. 1:3-29, Heb. 11:3, Acts 14:24-25, Rev. 4:11). But in the Mormon view of God, the universe is eternal and God simply reshapes and refines pre-existing materials.4 If this is so, then we again see that the god Mormonism affirms is not the God of Christianity. Therefore, we can quickly declare that Mormons fall outside the definition of Christian by their denial of these essential attributes of God.
http://www.pyracantha.com/Z/dualism.html 11/29/1995. Accessed: 4/15/2014.
2. Adams, Lisa Ramsey. "Eternal Progression." Encyclopedia of Mormonism.
http://eom.byu.edu/index.php/Eternal_Progression Accessed: 4/15/2014.
3 Robinson, Stephen E. "God the Father." Encyclopedia of Mormonism.
http://eom.byu.edu/index.php/Heavenly_Father Accessed: 4/15/2014.
4 Nielsen, F. Kent and Stephen D. Ricks. "Creation, Creation Accounts." Encyclopedia of Mormonism.
http://eom.byu.edu/index.php/Creation,_Creation_Accounts Accessed: 4/15/2014.