In a pioneering paper published two decades ago, Brent Lee Metcalfe demonstrated that after Martin Harris lost the first 116 pages of the Book of Mormon, Joseph Smith didn’t immediately start over from the beginning of the book. Rather, he picked up the dictation where he had left off, at the beginning of the Book of Mosiah. Only after translating from Mosiah to the end of the Book of Mormon did he come back to translate 1 Nephi through Words of Mormon. Metcalfe’s “Mosiah priority” hypothesis has gained wide acceptance from Mormon and non-Mormon scholars alike.
One of Metcalfe’s many arguments for the priority of Mosiah had to do with the Book of Mormon’s usage of the roughly synonymous terms “therefore” and “wherefore.” Metcalfe found that in the Doctrine and Covenants revelations dictated during the same period as the Book of Mormon, we observe a gradual shift from a preference for “therefore” in the earlier revelations to a preference for “wherefore” in the later ones. The same gradual shift can be seen in the Book of Mormon when the books are arranged according to a Mosiah-priority dictation order. Arranging the books according to 1 Nephi priority, by contrast, reveals a sharp discontinuity between Words of Mormon and Mosiah—precisely where the Mosiah priority hypothesis predicts a discontinuity should occur. A few years ago, I replicated Metcalfe’s analysis using a computer program I wrote that measures Book of Mormon word frequencies. The results are shown in the graph below.
This result is not by itself decisive proof of Mosiah priority, but it’s persuasive when taken in conjunction with Metcalfe’s other evidence. It should also be noted that this implies Joseph Smith was not simply passively reciting an English text he saw in his stone. Gradual changes in his prophetic voice would seem to imply that the job of translator was an active role.
To extend Metcalfe’s study, I performed the same analysis on a couple other pairs of synonymous terms and achieved comparable results. The first graph below shows the terms “whoso” and “whosever.” Note that under Mosiah priority, we see an initial exclusive preference for “whosoever,” followed by a side-by-side use of both terms in Helaman through Mormon, followed finally by an exclusive preference for “whoso” in the last-dictated portion. When the books are arranged according to 1 Nephi priority, by contrast, we see the same sharp discontinuity between Mosiah and the preceding books that we observed in the “therefore” / “wherefore” case. This provides strong additional support for the Mosiah priority hypothesis.
The other pair of words I looked at was “inasmuch” and “insomuch.” The results here are nowhere near as striking as the therefore/wherefore case, but still tend to support Mosiah priority. The overall trend according to Mosiah priority was toward a preference for “inasmuch” in the latter portions of the book, and this is consistent with the overwhelming preference for that term in the later sections of the D&C. By contrast, the trend according to 1 Nephi priority was in the opposite direction from that predicted by the D&C.
 Brent Lee Metcalfe, “The Priority of Mosiah: A Prelude to Book of Mormon Exegesis,” in New Approaches to the Book of Mormon (Salt Lake City: Signature Books, 1993), 395–444.
 The shift occurs predominantly in the Book of Ether. In the early chapters of Ether, “therefore” predominates. In the middle chapters, both words are used with more-or-less equal frequency. Near the end of the book, “wherefore” is dominant.
 Unfortunately, the D&C revelations dictated contemporaneously with the Book of Mormon don’t use either term. The instance of “inasmuch” in D&C 3:16 was a later insertion.