Symbolism, Imagery, Allegory
A little while after Paul confronts his parents about his past, his mom finally takes him clothes shopping. (She's been meaning to do it for months, of course.) And she feels so guilty that she lets him buy an entirely new wardrobe.
Paul is shocked: "Mom was out of control. She let me buy everything that I even thought about wanting" (3.13.97). Man, that's awesome. If it weren't for the years of neglect and the loveless childhood, we'd want her to be our mom, too.
When he gets home, he gives every single old outfit he owns to Goodwill (jackpot! We'll see you at the Goodwill store!), and fills his closet and drawers with the new things. In a way, he's shedding his old life—all the pain, loneliness, and despair—and making room for a brighter future. And some new pants.