While the boys on the island revert to primitive ways with their hunting, nakedness, and face painting, there is still one symbol of advancement, of innovation and discovery. Yes, that’s right, we’re talking about Piggy’s glasses. The boys find themselves at an utter loss for a way to start the fire. Jack mumbles something about rubbing two sticks together, but the fact is the boys just aren’t wilderness-savvy enough to do this. Because they aren’t equipped for roughin’ it for real, they have to rely on some remaining relics of their old world. So, of course, the glasses breaking mean they are in danger of losing touch with the civilized world they’ve left behind. With one lens broken, they’ve got one foot over the line.
But let’s also remember that the glasses are, in fact, a pair of glasses, primarily intended for looking through. Looking = vision, and vision = sight, and sight = a metaphor for knowledge. Piggy knows things the other boys don’t, like how to use the conch, and the necessity for laws and order. Part of the reason he gets so upset when they take his glasses is that, without them, he can’t see anything. “Seeing” is Piggy’s greatest attribute; it’s the one reason the boys don’t ostracize him completely; it’s the one way he’s useful. Without his glasses, then, he’s useless, something that no one wants to be.