Until then, he didn’t know how to read. Distressed by this inability, he retreated to the cave for months. Even this is interesting, for if this was about literal reading, why would he withdraw to a cave, when he could easily go to someone who could teach him how to read and write? Especially if we take into consideration the fact he was a merchant who had dealt with trade for so many years!
Taking things at a more surface value, certain people in the past deduced the Quran can only be a miracle if it was revealed through a Nabi who didn’t know how to read and write. Thus, without going into any depth, in fact even blocking the path to certain truths, they decided an unlettered Nabi was one who did not know how to read and write. As if this elevated the Rasul of Allah or made him greater in some way! All of this is the result of not duly knowing the sublimity of the Rasul and not understanding the reality of what he brought forth.
According to many, a Nabi who emerged from the middle of the desert must not know how to read and write in order for the amazing new perspectives he introduced to be considered a miracle. As if the miraculous aspect of what he brought would be reduced in any way had he known how to read and write!
Let us not forget we are bound to believe that Muhammad (saw) was the Rasul and the final Nabi of Allah. Believing in his ability to read and write has nothing to do with the pillars of faith.
The only reason Muhammad (saw) was called unlettered was because he was not of the People of the Book; this is the external meaning of being unlettered. In other words, he was not a Jew or a Christian who then became a Nabi and brought a new religious understanding.
There is also a more hidden, in-depth meaning to the notion of being unlettered, which is far more important!