Our eNotes site on Lear provides an excellent and direct answer to your question. Referring to a literary critic, Ian House, it begins "House emphasizes the dynamic relation between the main plot and the subplot in King Lear, proposing that the differences as well as the similarities between them unsettle and illuminate our understanding of the principal story. As the critic explains, the double plot universalizes the action by shifting emphasis away from individual characters and situations; the effect is more like that of a prism than a mirror, multiplying images rather than giving back a single one. Further, House analyzes the notorious implausibility of dramatic events in Lear, arguing that the absurdity is purposeful and heightened by the changes in the humorous tone of the subplot "from farce to melodrama, from domestic tragedy to surrealism." In the course of discussing these issues, the critic provides extended evaluations of Gloucester, Edmund, and, especially, Edgar.] click on the url below for the full discussion.