The admonition of Moroni 10:4-5 in the Book of Mormon simply encourages you to ask God if these things are not true. On the title page of the Book of Mormon near the bottom of the second paragraph we find this statement: "And now, if there are faults they are the mistakes of men." It is stated from the very start that the Book of Mormon probably has faults which are the mistakes of men;...."
First Nephi 19:6 heightens our suspicions as to whether the Book of Mormon came from God. "Nevertheless, I do not write anything upon plates save it be that I think it be sacred. And now, if I do err, even did they err of old; not that I would excuse myself because of other men, but because of the weakness which is in me, according to the flesh, I would excuse myself." This sounds like the gropings of man, not the positive statements of an all powerful God.
As we read on in the Book of Mormon this same groping theme becomes even more evident. Jacob 7:26 says in part: "And it came to pass that I, Jacob, began to be old; and the record of this people being kept on the other plates of Nephi, wherefore, I conclude this record, declaring that I have written according to the best of my knowledge...."
Now add the statement of Jarom 1:1, "Now behold, I, Jarom, write a few words according to the commandment of my father, Enos, that our genealogy may be kept" and it becomes apparent that what is being written was at the command of a mortal father, not God the Father.
Moving on to the statement of Mormon 8:1, "Behold I, Moroni, do finish the record of my father, Mormon. Behold, I have but few things to write, which things I have been commanded by my father" the same theme once again raises up before us.
Verse 12 of Mormon Chapter 8 casts even more doubt on the accuracy of this book when it says; "And whoso receiveth this record, and shall not condemn it because of the imperfections which are in it, the same shall know of greater things than these. Behold, I am Moroni; and were it possible, I would make all things known unto you."
Ether 5:1 says, "And now I, Moroni, have written the words which were commanded me, according to my memory;...." Not only did the command come from his mortal father, he also had no guarantee that what he wrote was accurate except for an imperfect memory!
Let us investigate further into what the Book of Mormon has to say about its origin. Second Nephi 26:15-16 tells us that "...the words of the righteous shall be written, and the prayers of the faithful shall be heard... For those who shall be destroyed shall speak unto them out of the ground, and their speech shall be low out of the dust, and their voice shall be as one that hath a familiar spirit..." In his comments on this passage LeGrande Richards, who was an apostle in the L.D.S. church, links 2 Nephi 26 with Isaiah 29 and says on page 69 of A Marvelous Work And A Wonder:
Old Testament law required that those that had a familiar spirit were to be stoned to death.
(Minor editing by Cooper Abrams)