So he disguises himself as Tom the beggar. The word "Bedlam" has been used to describe asylums in general. Soon after this term changed to "Tom O'Bedlam". That's why Edgar has now changed his identity as Tom. Dressed as a madman who begs and talks nonsense, Edgar thought he would be able to protect himself from Edmund and the law Edmund conspiratorially invoked. Edgar decides to "assume the basest and poorest form" in the form of the mad "poor Tom" out of self-preservation. The use of the superlatives "the vilest and the poorest" and the intensifier "the most" indicates that Edgar wants to destroy his own identity. The only "blanket" he reserves is the safest disguise for being a Bedlam beggar. The use of the superlative “lower” is significant; remember Edmund's soliloquy. Edgar, therefore, has taken on an element of Edmund's identity just as he has taken on his own