Composition is the naturalistic explanation for the Book of Mormon--the way books are always written--but it is at odds with the Joseph Smith of the historical record. The accounts of the neighbors picture an unambitious, uneducated, treasure-seeking Joseph, who had never written anything and is not known to have read anything but the Bible and perhaps the newspaper. None of the neighbors noted signs of learning or intellectual interests beyond the religious discussions in a juvenile debating club. To account for the disjuncture between the Book of Mormon's complexity and Joseph's history as an uneducated rural visionary, the composition theory calls for a precocious genius of extraordinary powers who was voraciously consuming information without anyone knowing it.While much remains unclear about how Joseph did the translation (was it really so literal or direct as some witnesses assumed?), all witnesses insist that it was a divine process of translation, not a work of composition. And that's consistent with the manuscripts that have survived, as Royal Skousen has masterfully demonstrated.
The transcription theory has Joseph Smith "seeing" the Book of Mormon text in the seerstone or the Urim and Thummim. He saw the words in the stone as he had seen lost objects or treasure and dictated them to his secretary. The eyewitnesses who described translation, Joseph Knight, Martin Harris, Oliver Cowdery, and David Whitmer, who was in the house during the last weeks of translation, understood translation as transcription. Referring to the seerstone as a Urim and Thummim, Knight said: "Now the way he translated was he put the urim and thummim into his hat and Darkned his Eyes then he would take a sentance and it would apper in Brite Roman Letters. Then he would tell the writer and he would write it. Then that would go away the next sentance would Come and so on." Joseph himself said almost nothing about his method but implied transcription when he said that "the Lord had prepared spectacles for to read the Book." Close scrutiny of the original manuscript (by a believing scholar) seems to support transcription. Judging from the way Cowdery wrote down the words, Joseph saw twenty to thirty words at a time, dictated them, and then waited for the next twenty to appear. Difficult names (Zenoch, Amalickiah) were spelled out. By any measure, transcription was a miraculous process, calling for a huge leap of faith to believe, yet, paradoxically, it is more in harmony with the young Joseph of the historical record than is composition.
(Bushman, p. 72)
Naturalistic explanations for the Book of Mormon are unable to explain how he could have written it, let alone why. And a severe obstacle for the composition/plagiarism theories is how Joseph could possibly have hoped to have gotten away with a fraud that involved so many witnesses - and why they all would go to their graves insisting that the plates were real and the translation was divine, even when some of them had fallen out with Joseph Smith.
Truly the Book of Mormon is a marvelous work and a wonder.