A Different Joseph Smith?
Do Mormons believe in a different Joseph Smith* to us?
The Mormon believes that Joseph Smith was a pre-existent being before his birth. She believes that Joseph Smith was a morally upright man who encountered an angel and became a prophet. She believes that Joseph Smith has now become or will become a god.
Is this a different Joseph Smith to the one that you and I believe in?
No. There is only one Joseph Smith who founded the Church of Jesus Christ of Latter Day Saints. This Joseph Smith was born in 1805 and died in 1844. There is only one Joseph Smith who married Emma Hale Smith in 1827. There is only one Joseph Smith who published the Book Of Mormon.
The fact that both the Mormon and I believe in the same Joseph Smith means that we can engage in dialogue about him. The Mormon can give me reasons to believe that Joseph Smith was a prophet. If they are convincing, they would affect my views on him. Likewise, I could give the Mormon reasons to believe that Joseph Smith was not an honest man. If she found them convincing, they would weaken her view that Joseph Smith was a prophet. If the Mormon and I believed in two ontologically parallel Joseph Smiths, this dialogue would be impossible (I am not necessarilly suggesting such a dialogue would be the most fruitful way to evangelize a Mormon).
In the same way, the Mormon and I believe in the same Jesus. We believe in the Jesus who was born of a virgin in Bethlehem, who spent his early years in Egypt, who worked as a carpenter, who performed miracles in Judea, who was crucified under Pontius Pilate and who was raised from the dead. There is no other Jesus who fits this description. We know who we are talking about, just as I know who the Mormon is talking about when she says "I believe that Joseph Smith is a true prophet." The Mormon has an utterly warped and heretical view of Christ's deity, but she believes in the same Jesus who lived in the first century who is the subject of the four Gospels.
If this Mormon comes to believe that she posesses eternal life through Jesus Christ by faith alone, without seeing the error of her heretical christology, she has not failed to put her trust in the name of Jesus. She has consciously believed in the same Jesus who spoke to the Samaritan woman at the well. For all we know, her christology may be more orthodox than the Samaritan woman's view of Jesus. Nevertheless, she has believed the offer of eternal life that is found in her own King James Bible. She would never thirst again.
*I am aware that there were actually five Mormon leaders called Joseph Smith. It is Joseph Smith Jr, the one who published the Book of Mormon that we are concerned with.