According to the theory of Jerry Ainsworth, Mormon was commanded to write the history of his own people, not any other (see Mormon 5:9-13). That being the case, the "beloved brethren" (Moroni 7:2) spoken of in the book of Moroni lay outside Mormon's parameters as a historian. Even if these people were Nephites, Mormon chose not to write about them because they were not a part of the Nephite nation. Moroni, on the other hand, was under no such constraint, and that may have been the reason he placed certain writings of Mormon in his own book. [Jerry L. Ainsworth, The Lives and Travels of Mormon and Moroni, p. 36]