Firstly, we must note that he is named Bastard in the script. Not Edmund. This speaks tot he philosophy of this character pretty easily. Although his true name is Edmund, he acts much more like a “base bastard” instead of a person. We also see him talking in verse before anyone enters. However, when his father enters, we see him talking to him in prose. Almost like Edmund is too dumb to understand verse so his father needs to dumb down his language.