Joseph Smith claimed, "We have imagined and supposed
that God was God from all eternity
I will refute that idea and take away the veil
so that you may see."
Now when he gives this sermon, I want you to imagine
you're a Latter-day Saint hearing this for the first time
Joseph Smith gets up and he says
We have imagined and supposed that God was God
from all eternity, and you're thinking
Now where have I imagined and supposed that?
I mean, Smith is addressing a thought that he knew was prevalent at that time
"You have imagined and supposed that God was God
from all eternity"
Where would we imagine this?
Well, I think we would have imagined it probably from reading the Old Testament
in Psalm 90 verse 2, it says, 
"Before the mountains were brought forth,
or ever you had formed the earth and the world
even from everlasting to everlasting you are God"
I'm reading from the Joseph Smith Translation here
So it's not that Mormons shouldn't know about this
The Bible makes it very clear that God was everlasting
Now, when you're talking to a Latter-day Saint
you need to be very specific about this
because just to say that God is eternal
is really no big deal in the conversation
because Mormonism teaches that man is eternal
according to the Doctrine and Covenants section 93
it says that man was in the beginning with God
We are eternal creatures, if you will
according to Mormonism
For a Mormon to tell you that they believe in the
eternal God really does not communicate anything
at this part in the conversation
What they need to explain to you is, well,
if he was eternal, do you believe he was eternally God?
Now that narrows it down
In that area a Mormon could not say yes 
because as Joseph Smith said,
"We have imagined and supposed that God was God
from all eternity, I will refute that idea
and take away the veil so that you may see."
And he goes on to explain how his God
the one that he represents
of whom he is a prophet for
was once a human being like us 
And he goes on to explain that in that sermon
What about this passage?
If all you had was the Book of Mormon
You would never understand what Joseph Smith
was saying in that sermon, that we quoted earlier
In Moroni chapter 8, verse 18, in the Book of Mormon
it says, "For I know that God is not a
partial God, neither a changeable being;
but he is unchangeable from all eternity
to all eternity." 
