FAQ

(*Possible spoilers*) In episode 1.8, "Ma's Holiday", one of the first indications that Isaiah Edwards couldn't read was his unwillingness to read to the Ingalls' girls from a storybook and this was confirmed in episode 2.12 "His Father's Son". Hard feelings are the result when the Edwards' adopted son, John Sanderson Edwards, writes his new father a heart-felt letter and an apparently uninterested Mr. Edwards lays it aside, unread. Matters are only resolved after Charles Ingalls tells John that Mr. Edwards didn't read the letter because he couldn't and was too proud to admit it . Although it was never completely discussed in this or any following episode, the closing scene just before the credits of "His Father's Son" shows John calling Mr. Edwards out of the family's treehouse for supper and, as he leaves, the camera zooms in on a copy of then-popular child's reader, the "McGuffey's Eclectic Primer - Revised Edition", lying on a small table in the treehouse. The logical conclusion would then appear to be that Mr. Edwards had been studying and, either on his own or with his family's help, was learning to read. Thus, if he persevered, by the time he took in the mute wild boy, Matthew, many years later in episode 9.6, "The Wild Boy, Pt.1", he should have been quite able to teach Matthew sign language by learning it himself from a book and this would fill in the perceived plot hole.