Symbolism, Imagery, Allegory
When Edgar disguises himself as "Poor Tom," he chooses to disguise himself as a naked beggar. Then, in the big storm scene, Lear strips off his kingly robes. Why might he do this, you ask? Is he just itching to feel the cool (er, freezing) air on his skin?
Nope. Lear has seen Poor Tom (naked) and asks, "Is man no more than this?" Then, presumably to find out if man is indeed "no more than this," he strips down to his birthday suit. What's up with that? Well, it seems that Shakespeare is making a point—that all men are vulnerable. In fact, man is nothing more than "a poor, bare, forked animal" (3.4.114-115). Donning rich and opulent clothing (like Goneril and Regan do), then, is merely a futile attempt to disguise man's true, defenseless nature.