If someone else wrote the Book of Mormon, why would they go to the effort of also supplying gold plates or require Joseph Smith to source them separately?

Any alternative theory of the Book of Mormon’s origin must not only account for how Joseph Smith produced all the words, but also account for the existence of gold plates.

Joseph’s claims about the Book of Mormon would be very different if he said he received the words as a revelation from God, but we know there were golden-looking plates which at least two dozen saw or even handled. These included Joseph Smith, Jr, the Three and Eight Witnesses, Emma Smith, Lucy Mack Smith, William Smith, Katherine Smith, Mary Whitmer, Josiah Stowell, Joseph Knight, Sr., Alva Beaman, and Martin Harris’s wife and daughter.

Some of the descriptions of the plates are as follows:

“[T]hey were fastened with rings thus [a sketch shows a ring in the shape of a capital D with six lines drawn through the straight side of the letter to represent the leaves of the record].” —David Whitmer (David Whitmer interview, Edward Stevenson diary, 22–23 December 1877)
“They seemed to be pliable like thick paper, and would rustle with a metalic [sic] sound when the edges were moved by the thumb, as one does sometimes thumb the edges of a book.” —Emma Smith (Emma Smith interview, The Saints’ Herald, 1 October 1879)

If Joseph didn’t have the education or expertise to write the Book of Mormon on his own and it was given to him by someone who did have the time and expertise, then how do we account for the gold plates?

It’s unlikely that someone would go to the effort to anonymously write a book and solely give it to Joseph Smith, and it seems even more unlikely that they would also supply (what appeared to be) gold plates with writing engraved on.

What would be their motive?

See:

Kirk B. Henrichsen – How witnesses described the plates

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