Symbolism, Imagery, Allegory
Imagine going out in public and realizing that you don't have a single scrap of clothing on. Does that sound like a nightmare you had once or a million times? Well, for Bobby Phillips, nakedness in public becomes pretty common, since once he wakes up invisible, it's the only way that he can get around without anyone noticing him. That makes it worth any discomfort and awkwardness that he feels:
But I think that maybe I get what the Greeks were up to. Because being naked outside, out here on the battlefield, it's like I've never been this charged up, this alert, this ready for anything. (9.5)
Bobby's nakedness serves, paradoxically, as a shield for him. Instead of making him vulnerable to the world (in the way that nakedness makes most people feel totally on view), Bobby's nakedness is what makes him invisible, it's what allows him to move around the world comfortably without drawing attention from anyone else. When he is naked, he can go wherever he wants without being seen by other people; he can move without fearing judgment or scrutiny.
In other words, walking around naked for Bobby is pretty much the exact opposite of how people usually feel when they're walking around naked on the street or in a public library. For more on how his invisibility turns his life into one long case of Opposite Day, be sure to read up on invisibility as a symbol elsewhere in this section.