Toward the end of Blood Meridian, the gang encounters a man whose brother is so severely disabled that he is kept naked in a cage. Obviously, this character cannot speak and does not contribute to the novel's dialogue.
Despite this, McCarthy mentions him frequently, and this "idiot" (as McCarthy describes him) is central to the narrative over the next couple of chapters. He is released, cleaned and dressed by women at the ferry encampment. Then, set free, he accompanies the Judge, at first willingly and later being lead like an animal with a collar and leash.
It seems unlikely that McCarthy would expend so many words on a character without meaning for readers to reflect on them to some extent. But I'm not clear on how the idiot - who is passive and vacant - fits into a novel about violence and religious philosophy?