A follow-up to this question, if the LDS church teaches that men can become gods, how does it reconcile this with the concept that there is only one God?
I am the LORD, and there is no other; apart from me there is no God. I will strengthen you, though you have not acknowledged me,
“You shall have no other gods before me.
I suppose if you wanted to split hairs, you could technically consider the LDS faith to be polytheistic, since Mormons believe God the Father, God the Son, and God the Holy Ghost to be separate and distinct individuals.
Outside of that, it's pretty simple. Mormons worship God the Father, through the Son. While we believe that there are other gods out there, they are not our God. I find that an analogy helps me think about this clearly: At work, I have one boss. He is my boss and no one else is. There are other bosses, but I do not report to them, they do not affect my quarterly reviews, and I don't really interact with them in any sort of manager-underling relationship. The same goes for God.
LDS doctrine reconciles the two concepts quite easily, in fact. From Moses 1:35:
But only an account of this earth, and the inhabitants thereof, give I unto you.
The revelations we are given are limited in scope to this world and the people living on it, and how they can find salvation. And within that scope, they are correct. Any knowledge beyond that does not affect us, nor does it have any bearing on where we'll end up spending eternity, so we don't really need to worry about it; we've already got our hands full with trying to live up to the basics!
When considering this kind of question, it is good to have a correct idea of the meaning behind the words involved. According to the NOAD, polytheism is defined as "the belief in or worship of more than one god." While Mormons believe that people are children of God the Father and therefore have the potential to be exalted as godlike beings, their worship in this life and the next is directed toward only one being, God the Father (whether this is the same God as Jesus Christ and the Holy Ghost can be discussed elsewhere).
An excerpt from an official LDS Gospel Topic Essay titled "Becoming Like God":
Does belief in exaltation make Latter-day Saints polytheists?
For some observers, the doctrine that humans should strive for godliness may evoke images of ancient pantheons with competing deities. Such images are incompatible with Latter-day Saint doctrine. Latter-day Saints believe that God’s children will always worship Him. Our progression will never change His identity as our Father and our God. Indeed, our exalted, eternal relationship with Him will be part of the “fulness of joy” He desires for us.
Latter-day Saints also believe strongly in the fundamental unity of the divine. They believe that God the Father, Jesus Christ the Son, and the Holy Ghost, though distinct beings, are unified in purpose and doctrine. It is in this light that Latter-day Saints understand Jesus’s prayer for His disciples through the ages: “That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us.”
I don't have time for a well researched answer right now, but I want to offer two quick thoughts:
LDS doctrine refers to a "Godhead" consisting of three distinct individuals: God the Father, God the Son, and God the Holy Ghost. Because they are perfectly united in purpose and goodness, we refer to them as one God. Jesus taught this concept by saying that all who know him know the Father and by saying that he only does what the Father sent him to do.1 We follow Jesus' example and only pray to the Father and only worship the Father. There is no other God outside of His power and authority.
God the Father is the ruler of the universe. As His children, He is willing to share His power with us and make us like Him should we prove our willingness to obey His will. But we will always recognize Him as our Lord and Father just as Jesus does.2 In this way we wholeheartedly accept the commandment that we shall have no Gods before him.
I wanted to quickly contribute to the discussion even though I don't have time to find these concepts explained anywhere authoritative. Hopefully someone else can fill in the gap.
I believe the best way to answer this question is to give LDS interpretation on all of Isaiah chapters 40-48. There are many verses that discuss there being only one God. I will start by discussing the purpose of these verses being written. Isaiah is speaking to many people who are looking to "Other gods" to be saved. People are trying to create their own Gods, and overall turning from their God. People often interpret these verses as there is only one God in exhistance, but LDS interpret them as there is only one God who we can turn to to be saved. I will give an example.
Isaiah 43:10 Ye are my witnesses, saith the LORD, and my servant whom I have chosen: that ye may know and believe me, and understand that I am he: before me there was no God formed, neither shall there be after me. 11 I, even I, am the LORD; and beside me there is no saviour. (KJV)
LDS interpretation is based on the subject being reffered to, or in other words the idea of going to other gods to be saved. It is specified in verse 11 that there is no savior. In other words it is interpreted by LDS that we only have one God we can turn to to be saved. One God that is our God.
Some verses that add a better definition to the phrase "No God beside me" are
Isaiah 47:8 Therefore hear now this, thou that art given to pleasures, that dwellest carelessly, that sayest in thine heart, I am, and none else beside me; I shall not sit as a widow, neither shall I know the loss of children:
10 For thou hast trusted in thy wickedness: thou hast said, None seeth me. Thy wisdom and thy knowledge, it hath perverted thee; and thou hast said in thine heart, I am, and none else beside me.
Based on these verses it adds a second meaning to the phrase. When used here only a few chapters later it isn't meant the mean the only one in existence, but the greatest, or most powerful. "none else beside me" can be taken to mean that none can overthrow, or none can challenge.
Due to shortness of time I cannot give a long answer but I may add to this one in a few days. I hope this at least helps put that interpretation in context.
For a more detailed answer this site has good information on the subject: http://en.fairmormon.org/Mormonism_and_the_nature_of_God/%22No_God_beside_me%22
While members of the LDS church believe in three separate and distinct members of the Godhead (God our Heavenly Father, Jesus Christ, and the Holy Ghost sometimes called the Holy Spirit), therefore making us seem polytheistic by the definition given by brandaemon, we are still monotheistic in worship.
To give a little bit more insight to resplin's comment, despite the seemingly paradoxical existence belief in the Godhead with canonized scripture, it is, in fact, in complete accordance and agreement with it. 2tim424 made a comment on Dave DeLong's post questioning how his answer works with scriptures referring to only one God.
Christ testified of the existence of the Father on multiple occasions (John 10:36; John 17:3; Matt. 6:9-13) and the Father has testified of the Son as well both at Christ's Baptism in Matt. 3:17 and on the Mount of Transfiguration in Matt. 17:5, Mark 9:7 and Luke 9:35 and the Holy Spirit is referred to as well at Christ's Baptism in Matt. 3:16 and when Christ is describing the desire of the Father to bless His children with it if they will ask Him in Luke 11:13.
Now that we have established the existence and basis for the core belief as described in the New Testament we can answer the questions about the scriptures that seem to point to only one God. When Christ was called "Good Master" by one seeking knowledge about how to gain eternal life, Christ told him, "Why callest thou me good? there is none good but one, that is, God" (Matthew 19:17 KJV) and he repeatedly counselled His disciples to pray unto the Father (Matt. 6:9, Luke 11:2; 3 Ne 13:9).
The other part of all of this is in the time period surrounding the Atonement. First, when Christ prayed to Heavenly Father the great Intercessory Prayer (John 17) He spoke with Heavenly Father in giving an accountability and report of what He had accomplished on earth. He said, "I have finished the work which thou gavest me to do."(John 17:4) indicating that His earthly mission was given to Him by the Father and part of a larger plan that the Father was in charge of. This idea that Christ answers to, and serves, God the Father is made more evident both in the Garden of Gethsemane and on the Cross at Calvary.
In the Garden, as He atoned for the sins of the world, He prayed to the Father, "Father, if thou be willing, remove this cup from me: nevertheless not my will, but thine, be done"(Luke 22:42 KJV) giving the impression that the Father was in charge of what was happening. On the cross he cried out to the Father, "My God, My God, Why has thou forsaken me?"(Matt. 27:46; Mark 15:34) as well as "Father, into thy hands I commend my spirit" (Luke 23:46) and what would logically follow, "It is finished" (John 19:30). It should be noted that the order in which He said these things is not known, and it is not confirmed that The last statement was directed to Heavenly Father, but logic lends itself to it, as it is the only account withing the gospels that doesn't specify the last words of the Savior being directed towards the Father.
Christ was very clear about His accountability to God the Father and it is a well known fact that the Holy Spirit serves God the Father as well. So, when Christ says that "there is none good but one, that is, God"(Matt 19:17 KJV) and Isaiah reads "there is no God besides me" (Isaiah 45:5) we can agree wholeheartedly, because God the Father is the Father of our Spirits and He is the One God that is spoken of. This is the extended explanation to Dave DeLong's analogy and how it is in accordance with the other scriptures pertaining to one God. As for the part where men become gods, there is a bit more explanation needed.
He, being our Father, desires the best for us, His children. According to LDS doctrine, that means perfection and so He created a plan whereby we can become like Him. This plan required the Atonement of Jesus Christ (including the Garden of Gethsemane, the Crucifixion and Resurrection) for us to be able to return to, and be perfected in, Him if we will keep His commandments and endure to the end.
Paul described our potential to become like God in Romans when He said,
"The spirit itself beareth witness with our spirit, that we are the children of God: And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together." (Romans 8:16-17)
Latter-day prophet Lorenzo Snow taught this doctrine quite powerfully as he related this experience:
"In the spring of 1840, Lorenzo Snow was in Nauvoo, Illinois, preparing to leave for a mission in England. He visited the home of his friend Henry G. Sherwood, and he asked Brother Sherwood to explain a passage of scripture. “While attentively listening to his explanation,” President Snow later recalled, “the Spirit of the Lord rested mightily upon me—the eyes of my understanding were opened, and I saw as clear as the sun at noonday, with wonder and astonishment, the pathway of God and man. I formed the following couplet which expresses the revelation, as it was shown me. … “As man now is, God once was: As God now is, man may be.”1 Feeling that he had received “a sacred communication” that he should guard carefully, Lorenzo Snow did not teach the doctrine publicly until he knew that the Prophet Joseph Smith had taught it.2 Once he knew the doctrine was public knowledge, he testified of it frequently." (Teachings of the Church: Lorenzo Snow, Chapter 5: The Grand Destiny of the Faithful)
As for the doctrinal explanation and support of this, you can read the rest of that chapter here: Teachings of the President of the Church: Lorenzo Snow, Chapter 5: The Grand Destiny of the Faithful
This should answer most, if not all, additional questions concerning this, but if not, please feel free to ask them.
As a seventh generation Mormon I do not agree with other Mormons that say there are many Gods but only one God for us. I believe it is more accurate to simply say: There is only One true God, but that God is not just one finite personage. God refers to an infinity of divine finite beings like Jesus and Abraham and Sarah that are in John 17 type unity. The Creating Godhead for our earth are three finite beings in that Union. Jesus truly is the Son of God the Father. That means he will continue and become a God the Father on a future earth. It means his Father was once a Son on a previous earth, with a Father before him. There is no beginning and there will be no end to this Lineage of divine beings. Those that become Joint heirs with Christ are also in this lineage. All divine finite beings in this lineage are in a state of eternal progression. But the infinite Union of these beings is not: it has tri-Omni power and is ever-existing and unchanging.
